Capsule colors, opacity, and titanium dioxide free. How a capsule gets its color, and how to specify one

How are capsules made opaque without titanium dioxide?

Mostly with calcium carbonate, at a loading several times higher than the titanium dioxide it replaces, and the result is semi-opaque rather than opaque. Two other routes exist. Gelatin can be whitened with dissolved phosphate or citrate salts that crystallize in the film, and colored capsules can be made opaque with iron oxide pigments instead of a white base.

The reason titanium dioxide was in nearly every opaque capsule is physics. A shell goes opaque when light scatters at the boundary between particles and the polymer around them, and the scattering gets stronger the further apart the two refractive indices sit. Gelatin and HPMC sit near 1.5. Titanium dioxide sits at about 2.5 to 2.7 depending on the crystal form. Calcium carbonate sits at about 1.58, talc at about 1.5 to 1.6, hydroxyapatite at about 1.65. So titanium dioxide scatters hard and the others scatter weakly, which is why a white gelatin capsule needed only about 2% titanium dioxide by weight and the replacements need more. One European maker's data sheet for a standard white size 0 puts titanium dioxide at 2.00%. The patent behind one large maker's calcium carbonate HPMC capsule claims 3% to 10% by weight, preferring 5% to 7%.

Table 1. The four ways to make a shell opaque. Refractive indices are pigment reference values. Loadings and performance are from maker patents and the 2024 industry study for the European Medicines Agency, not from our bench.

The measured comparison worth knowing comes from the calcium carbonate patent's own examples. An HPMC film with 2.0% titanium dioxide had a contrast-ratio opacity of 63% and let 0.7% of light through at 650 nm. The same film with 10% precipitated calcium carbonate had 33% opacity and let 7.9% through. Five times the loading, about half the opacity, about ten times the light transmission. That is the trade the market has made, and the reason the word "semi-opaque" appears on most makers' TiO2-free product pages.

Capsules.com supplies HPMC and gelatin, our opaque shells are made without titanium dioxide, and the white is a calcium carbonate white unless a specification says otherwise. Our gelatin capsules are bovine, from hide or bone, and the material comparison covers what gelatin and HPMC shells are made of.

Is titanium dioxide banned in capsules?

In food and food supplements in the EU, yes, since 7 August 2022. In Great Britain, the US, Canada, Australia, New Zealand, and in medicines everywhere, no. So an opaque white capsule is two different products depending on where the finished product is sold, and a brand that sells on both sides of the Channel has one lawful choice for both, which is the titanium-dioxide-free grade.

Table 2. Titanium dioxide in a capsule shell, by market and use. Status at September 2026. The supplier qualification article sets out where the regulations disagree on titanium dioxide, with the legal citations, and the claims article covers what the ingredient list has to say.

The medicines line matters for anyone reading pharma trade press and assuming the ban reached them. The European Medicines Agency's 2024 review found the alternatives inferior and replacement feasible for under 5% of authorized medicines, and the Commission's August 2025 working document said the use should be maintained. Roughly 91,000 human medicinal products in Europe contain titanium dioxide. So a licensed medicine in Europe can still ship in a titanium dioxide capsule. A food supplement in the next aisle cannot.

Our position is one grade for everyone. The number of customers who sell into the EU, or who might, is large enough that carrying a titanium dioxide grade for the markets that still allow it would mean two whites on the shelf and a mix-up waiting to happen on someone's line. If you need a titanium dioxide capsule for a medicine, tell us and we'll say who to call.

Does a TiO2-free white capsule look the same?

Not quite, and the difference is measurable. Put a calcium carbonate white next to the titanium dioxide white it replaced and you'll see a softer, slightly translucent shell that reads as natural or chalky rather than bright. The industry study for the European Medicines Agency measured the color difference between a titanium dioxide capsule and the TiO2-free version from the same maker and product line at above 2 delta E, and the usual rule in coating work is that a difference above about 2.5 is visible to the naked eye. Different makers land in different places on that scale.

Three other differences showed up in the same study, which tested 13 TiO2-free shells from four makers. All 13 were worse than their titanium dioxide references at hiding what's inside the capsule. The calcium carbonate shells were more brittle at 0% relative humidity, in both gelatin and HPMC, which matters in a dry winter room (see what happens to capsules in a dry room). And under light stress the calcium carbonate shells got whiter, while a pink shell colored without iron oxide bleached to white.

None of that makes the TiO2-free white a poor capsule. Disintegration and dissolution published by the makers are the same as the titanium dioxide grades, within 15 minutes for disintegration and matching profiles at pH 1.2 and 6.8. What it means in practice is three things. Look at a physical sample before you approve artwork, because a rendering of "white" won't show you the shade. Don't specify a white capsule as the light protection for a photolabile fill. And if your product used to ship in a titanium dioxide white, expect the consumer to see a change and decide whether to say so.

Transparent, translucent, or opaque. Which do I want?

Pick clear if the fill looks good and isn't light sensitive, opaque if you need to hide the fill or protect it, and translucent if you want color without hiding the fill entirely. The words mean different things at different makers, so it's worth pinning them down.

Clear, also called transparent or natural, is the shell with no colorant and no opacifier. Gelatin gives a glassy, polished look. HPMC used to be hazy next to it, and the current gelling-agent-free HPMC grades are close enough that most people can't tell them apart in the hand. A clear shell shows the fill's color and texture, which sells well for a herb blend, a collagen powder, or a bead formulation. A clear shell also shows the fill level, so a half-empty capsule looks half empty, and it shows powder segregation if a blend separates.

Translucent is a dyed shell with no opacifier. Light gets through, the fill is partly visible, and the color reads as tinted glass. Most natural-colorant capsules are translucent because the colorants that make them are dyes, not pigments.

Opaque hides the fill. With titanium dioxide gone from EU food, "opaque" on a TiO2-free data sheet usually means semi-opaque, so ask for a sample against a dark fill before you rely on it. The reasons to go opaque are the ones you'd expect. The fill is an unappealing brown or gray. The fill is light sensitive. The product needs to look the same as a competitor's or a previous version. Or the capsule is for a clinical study and has to hide a tablet inside it, and the clinical trials article covers which capsule color hides a tablet.

One large maker's customer survey found that a large majority of its food and pharma customers rated the availability of opaque capsules as very important. Opaque is the default expectation for a white supplement capsule, and in EU food "opaque white" now means calcium carbonate semi-opaque.

Do opaque capsules protect a light-sensitive fill?

Opaque colored capsules made with iron oxide do. Calcium carbonate white does not do much, and a clear shell gives none. If light protection is the reason you're choosing an opaque capsule, choose the pigment, not the word.

The industry study for the European Medicines Agency exposed three model drugs in different shells to light and ranked the shells by how well the drug survived. Titanium dioxide and iron oxide shells came out level at the top. The sodium phosphate white gelatin came next. Calcium carbonate white and the clear shell came out level at the bottom. In tablet coating, where the same pigments are used, 0.2% yellow iron oxide in an uncoated tablet gave more light protection than an 11% coat of a titanium dioxide white, and 1% to 1.5% red or yellow iron oxide in a film coat gave 75% to 85% photoprotection, with 2% or more red iron oxide close to complete.

So the practical order, from most to least protective, is a red, yellow, brown, or black iron oxide shell, then a titanium dioxide white where you're still allowed one, then a salt-whitened gelatin, then calcium carbonate white or a dyed translucent shell, then clear. If your fill is photolabile and your brand wants white, the answer is usually an opaque secondary pack, an amber bottle, or a blister, and the capsule stays white.

Two caveats. Black iron oxide gave no significant protection in the coating study even though it looks the darkest, because its protection comes from absorbing rather than scattering and the loading is low. And the light limit in USP <671> (no more than 10% transmission between 290 and 450 nm) is a container test, not a shell test. No maker we found publishes a transmission spectrum for its shells by color, so treat a "light protective" claim on a color chart as a claim until you've seen the curve.

What are capsule colors made from?

Two families. Dyes, which dissolve in the gelatin or HPMC solution and give a clear tinted shell, and pigments, which stay as particles and give an opaque one. Most capsule colors are one of three iron oxides, a handful of synthetic food dyes, or a natural extract, sometimes blended with a white base.

The colorant goes into the dip solution at the start of the process, along with the opacifier if there is one and a trace of surfactant, before the pins are dipped. That's why the color runs through the whole shell rather than sitting on the surface, and why a color change at the maker is a formulation change and not a coating change. How empty capsules are made walks through the eight steps.

Table 3. The colorant families used in capsule shells. What each one gives you and the trade-offs, from maker technical notes and colorant supplier data.

Blue and green deserve a sentence of their own, because the question comes up on most branding calls. There is no iron oxide blue or green. A blue opaque capsule is a dye (indigo carmine or brilliant blue, or spirulina) over a white base. A green one is a blue dye plus a yellow, or chlorophyllin in the EU. Which means a blue or green shell carries the dye rules in the next section and can't lean on the iron oxide exemptions.

Which colorants are allowed in the US, the UK, and the EU?

The same short list of iron oxides, carmine, riboflavin, caramel, and a few plant extracts is permitted in capsule shells on both sides of the Atlantic. The synthetic dyes are where the markets differ, and where the rules are moving.

Table 4. Colorants in capsule shells for food supplements, by market. The claims article owns what the finished product's label has to say. This table is about what can go in the shell.

Three things in that table decide more specifications than the rest of it.

First, the iron limit. Iron oxides are the best pigments a capsule can have, and the US caps the elemental iron from a labeled daily dose at 5 mg for supplements and for ingested drugs. A pale color at two capsules a day is nowhere near it. A deep red or a black at six capsules a day can be, and the industry study for the EMA put the practical limit at about three size 0 capsules a day for a fully opaque iron oxide shell. Ask the maker for milligrams of elemental iron per capsule and do the arithmetic against your dose.

Second, the warning. In the EU and Great Britain, a food that contains any of tartrazine, quinoline yellow, sunset yellow, azorubine, ponceau 4R, or allura red carries the words "may have an adverse effect on activity and attention in children" after the color's name. Food supplements are on that list of foods. Most brands would rather not print that sentence, which is why a European blue capsule is usually indigo carmine or brilliant blue and a European yellow is usually riboflavin, curcumin, or an iron oxide. For a medicine the same six appear in the EMA excipient annex with a leaflet statement, "may cause allergic reactions."

Third, the US phase-out. The FDA revoked Red 3 in January 2025 and announced in April 2025 that it wants the six remaining petroleum-based dyes out of the food supply by the end of 2027. As of September 2026 that rests on voluntary pledges from food companies rather than a rule, and no rule revoking Blue 1, Blue 2, Red 40, Yellow 5, Yellow 6, or Green 3 has been proposed. No rule stops a capsule maker using them today. What has changed is the direction. A brand launching a blue capsule in the US in 2026 on FD&C Blue 1 should ask itself whether it wants to reformulate the shell in 2028, and a February 2026 FDA letter now lets a product say "no artificial colors" if the only colors in it are the exempt ones, which for a capsule means iron oxides, spirulina, and the plant extracts. The claims article covers the "no artificial colors" wording.

Can I use natural colors in a capsule?

Yes. Several makers offer HPMC capsules colored only with spirulina, chlorophyllin, safflower, annatto, caramel, or purple sweet potato, with no titanium dioxide and no calcium carbonate. What you give up is fastness and consistency, and you should know how much before the brand guide is signed.

Natural colorants are dyes, so the capsule is translucent unless a white base is added. Several of them are unstable in ways that matter on a shelf. Anthocyanins, the purple and red from grape skin or purple carrot, hold their color only below about pH 3.5 and drift toward blue above it. Curcumin is sensitive to light and to alkaline conditions. Spirulina blue is the fragile one. One colorant supplier's light test kept only 4% to 24% of spirulina's color after 15 days under continuous light depending on pH, against 99% for butterfly pea and 53% to 61% for anthocyanin reds. Carmine is the stable natural red, and it's from an insect.

Batch-to-batch shade is the second cost. A synthetic dye is the same molecule every time. A plant extract varies with the crop, so one maker warns of "variations in color from one batch to the next" on its natural line, and a reseller says there's "a high chance of variability in the hues" between batches. If a retailer photographs your product for a listing, that variability ends up on the page.

The third cost is money. Natural colorants need higher loadings and more stabilization, and the makers price them accordingly. None of that argues against them. It argues for a physical sample kept in the office window for a month before launch, a shade tolerance agreed with the maker in writing, and an opaque bottle.

Can a capsule be matched to a Pantone color?

Closely. Not exactly, and anyone who promises "the exact Pantone" on a capsule is describing a target rather than a result. The maker's colorist mixes dyes and pigments toward your reference, dips a sample film or a short run of capsules, and sends it for approval. You approve a physical standard, and future lots are matched to that standard rather than to the printed swatch.

Three things stop a shell from hitting a printed Pantone number. The Pantone formula guide is ink on white paper, and most of its colors are translucent by design, with the white paper showing through. A capsule's substrate is a curved, glossy film of gelatin or HPMC, which is either clear or a calcium carbonate off-white, and the same dye over each gives a different color. And the permitted colorants differ by market, so a match built with a dye you can use in the US may need rebuilding with iron oxides for Europe, and it won't land in the same place. Makers say this in their own words. One large maker notes that a color proposal is "assessed against applicable standards for the intended marketing regions" before it's offered.

So ask for four things. A physical sample of the assembled capsule, cap and body together, in the material and opacity you'll buy, because a flat film reads differently from a curved shell and some makers approve on film. The colorant list behind the sample, with E numbers or 21 CFR sections, so regulatory can check it before you fall in love with the shade. A written tolerance, in delta E or in words, that both sides will accept on future lots. No capsule maker we found publishes one, so it has to be agreed. And confirmation that the maker retains the approved standard and matches your repeat orders to it, so the third order looks like the first.

One rule of thumb from adjacent industries. Printers and plastics decorators usually treat a delta E of about 2 as a good commercial match and about 2.5 as the point where most people can see a difference side by side. A capsule is small, curved, and rarely seen next to its swatch, so a little more latitude than that is normal, but write the number down.

What's the minimum order for a custom color, and how long does it take?

Published minimums for a custom color run from about 350,000 capsules at the low end to 1.5 million, 2 million, or 5 million at makers and distributors, and the time from Pantone reference to capsules on your dock is measured in weeks. A custom color is a factory run made to order, so the minimum is the factory's and so is the lead time.

Table 5. Custom color minimums and lead times, as published by sellers. Each row is one seller's published figure, not an industry rate. Sources in the footnotes. Capsules.com quotes custom colors individually.

None of those sellers publishes the deposit or the matching fee, and only one seller says whether the minimum is per color per size. Assume it is, because the machine runs one color at a time and a size change is a change of pins. So a brand wanting a custom two-tone in sizes 0 and 00 is asking for four color runs, not one. Custom colors are quoted individually and carry a deposit, at Capsules.com and at most sellers, because the capsules have no other home if the order falls through.

The alternative most brands should look at first is a standard color. Standard colored and two-tone capsules exist at the reseller level in boxes of 75,000 to 100,000, at one US reseller for about 58% more per box than the same size in clear. The palette is short, the shade is the maker's and not yours, and the same red is on other people's products. In exchange you get capsules in days rather than months and no deposit. If your brand color is close to a standard color, ask for a sample of the standard one before you start a custom project.

What's a two-tone capsule, and is it worth it?

A two-tone capsule has a cap in one color and a body in another. Red cap, black body. White cap, blue body. Clear cap, colored body so the fill shows at one end. Makers offer it because the cap and the body are made on separate pin bars and joined afterward, so giving them different colors costs a second dip solution and nothing else on the line.

Two-tones do real work in three places. They tell dose strengths apart at a glance, which is the use pharma cares about and the FDA's medication error guidance points at when it says multiple strengths "ideally should look different from each other." They give a brand a signature without a custom color, since a standard white body under a standard blue cap is a combination and not a bespoke shade. And in sports nutrition the black-and-red pre-workout capsule has become a category look, which is a reason for and against it depending on whether you want to sit in the category or stand out of it.

The costs are the ones you'd guess. Two colors means two colorant declarations on the ingredient list, two shades to hold within tolerance, and for a custom two-tone, two color runs against the minimum in Table 5. If your product comes in three strengths and each has its own two-tone, that's six colors to control and a mix-up risk in the warehouse, which is why some manufacturers use the cap color alone to mark strength and keep one body color across the range. Standard two-tones exist at resellers in the common combinations, sold either joined or as separated caps and bodies for a manual plate.

There's also a third color option. Some makers band the join between cap and body with a colored gelatin or HPMC band, which is done for tamper evidence and liquid fills more than for looks, and it adds a third declared colorant.

Can I print my logo on a capsule?

Yes. Capsules are printed after they're made, on an offset printer that transfers edible ink from an etched plate to a roller to the shell. You can print along the length of the capsule (axial) or around it (radial), on the cap, the body, or both, in one or two ink colors, with the print aligned to the capsule's orientation (rectified) or not. One large maker offers radial print up to 320° of the circumference and several lines of axial text. One Japanese maker says more than 90% of the pharmaceutical capsules it makes are printed.

The ink is where the specification questions live. Edible capsule inks are a binder, a colorant, and a solvent that evaporates, with about 1 to 3 µL of ink per capsule. The binder is shellac or hypromellose. Shellac (E904) is a resin from the lac insect, so a capsule printed in a shellac-based ink isn't vegan even if the shell is, and one large maker's vegan certification covers printed capsules only when the ink is shellac-free. The ink colorant is a lake, a dye, or an iron oxide, and white inks have historically used titanium dioxide, which puts the same EU food question on the print that sat on the shell. Ask for the ink's full composition and treat it as an ingredient, because the ingredient list has to. The claims article also covers what that does to a vegan, halal, or kosher claim.

Print minimums are higher than custom color minimums at the sellers who publish them, 1 million to 5 million capsules depending on complexity, with artwork approval and a plate to make before the first run. No seller we found publishes a plate or setup fee. Pre-printed standard designs exist at the small end for hobby quantities and aren't relevant to a brand. As with color, printing is a project with a proof, a physical sample, and a written tolerance, and it's quoted individually.

Does capsule color change how the product is taken?

The published research says color changes what people expect from a capsule, and the practical use of that finding is telling strengths apart rather than selling. A 1996 review in the BMJ of 12 studies found red, yellow, and orange associated with a stimulant effect and blue and green with a calming one, with inconsistent results on whether the color changed the measured effect. A 2022 survey across five countries found about 40% of people expected a sedative to be blue, 43% expected a stimulant to be red, and 50% expected pain relief to be white. Sedatives and anxiolytics in the review's sample were more likely than antidepressants to be green, blue, or purple.

That is about expectation, and the use of it for a supplement brand is to avoid fighting the reader. A sleep product in a red capsule and a pre-workout in a pale blue one each ask the consumer to override a habit. That research says nothing about what the capsule's contents do, and this page doesn't either.

The use with a paper trail behind it is differentiation. Regulators and safety bodies ask that different strengths of the same product look different, because a look-alike pair is how a double dose happens on a nightstand. Color is the cheapest way to do that, and a two-tone or a cap color per strength is the usual method. For compounding, where a pharmacist may be filling three strengths by hand in one week, the same logic applies, and the compounding article covers using a different capsule color for each strength.

What should the color lines in my capsule specification say?

Nine lines. Material and size you already have from the capsule size chart. The color block sits under identity in the specification, and what a capsule specification contains shows where.

Table 6. The color block of a capsule specification. Write each line as a value, not a description, so the certificate can be checked against it.

Ask the maker for the colorant declaration as a document, not an email, and file it with the specification. The declaration answers a line in the capsule supplier questionnaire.

What changes when I change a capsule color?

More than the artwork. A color change at the capsule is a change to the finished product's ingredient list, to its stability file if the shell's light protection changed, to its retailer listing images, and for a licensed medicine in the US, to its approval. The switching article covers the general change control write-up. The color-specific consequences are these.

The ingredient list moves. A new colorant appears, an old one goes, and in the EU a Southampton six dye arriving or leaving adds or removes the warning sentence. In the US, a switch from an FD&C dye to iron oxide can unlock the "no artificial colors" wording, and a switch the other way removes it.

The claims move. Carmine in, vegan out. Shellac ink in, vegan out. A pearl white that carried titanium dioxide can't cross into EU food.

Light protection may move. From an iron oxide opaque to a calcium carbonate white is a real drop in photoprotection, and a product whose stability data was generated in the old shell should be re-read against the new one before the shelf life is carried over. The storage article covers what the auditor expects you to record.

For a US drug, a color change is not a like-for-like. The FDA's own procedure classes "any change in capsule composition or appearance, including change in size, color or dye" as a prior approval supplement, and Health Canada treats a change of opacifier as notifiable. FDA's May 2025 draft guidance, Replacing Color Additives in Approved or Marketed Drug Products, proposes letting a color additive replacement go in as a CBE-30 supplement instead, but it is a draft and not yet final. A supplement doesn't carry that filing, but a quality system under 21 CFR 111 or BRCGS still expects a change record, and the switching article has one to copy.

Finally, the consumer notices. A white that went from bright to natural, or a blue that went from a dye to spirulina, will look different in the bottle, and reviews mention it. Decide in advance whether the pack says why.

Color and opacity spec checker

Answer eight questions about the product and the markets it sells in, and the checker writes the color block of your specification, lists the flags that apply to your choices, and gives you the questions to send your capsule maker. Nothing you enter leaves the page. The prompt pack below does the same job in your AI assistant, with the reference data attached and room to work through the trade-offs. Get the AI prompt pack.

What is an AI prompt pack?

An AI prompt pack is a small set of files you load into the AI assistant you already use. The assistant then asks you the right questions, works through them with you using our reference data, and shows its working as it goes. We publish one with each article. We did the prompt engineering so you don't have to. Each prompt has been engineered so it asks the right questions in the right order, carries the reference data it needs, and says plainly what it doesn't know.

Inside the Capsule Color and Opacity Spec AI Prompt Pack is a prompt file that turns your assistant (Claude, ChatGPT, Gemini, Grok) into a color specification writer for empty capsules, a workbook it fills in as you go, and a reference sheet with the colorant tables from this page, the market rules, and the published minimums. It walks you from brand intent to a specification block, the maker brief for a Pantone match, the ingredient list consequences by market, the iron arithmetic against your dose, and the change record if you're moving from a color you already have.

Why a pack and not just a table? Because the right answer depends on your markets, your claims, your dose, and your brand, in that order, and a table can't ask which comes first. It's the conversation we'd have with you on a call, packaged so you can have it at your desk with your Pantone reference and your label in front of you.

Use the form below to request this resource. Newsletter updates are a separate, optional choice.

Get the Capsule Color and Opacity Spec AI Prompt Pack

If you'd rather talk it through, reply to any email from us or write to us through the contact page. A person who has specified capsule colors into products and argued with a colorist about delta E will get back to you. If you want to see our white against your own fill, ask for a sample box.

Related.

• Gelatin vs HPMC capsules. Which to use, and why
• Vegan, halal, kosher, and allergen claims for capsules
• How to qualify an empty capsule supplier
• What a certificate of analysis and a specification contain
• Capsules for compounding
• Capsules for clinical trials. Placebo, over-encapsulation, blinding sizes, and the paperwork

Sources.

• Opacity and refractive index. Wikipedia, Opacifier; Natural Pigments, white pigments reference (refractive indices): https://www.naturalpigments.com/artist-materials/white-pigments. US patent 11,517,535 (calcium carbonate HPMC capsule, priority 2018, granted 2022) and its examples, patents.google.com/patent/US11517535B2; US application 2022/0218619 (soluble salt white gelatin capsule); EP 4309649 A1 (zinc oxide and calcium carbonate shell). Guinama technical sheet, white size 0 capsules (TiO2 2.00%): https://www.guinama.com/documentacion-tecnica/93289_FT-Capsules-0-white-EN-Laboratorios-GUINAMA.pdf. Lonza Knowledge Center, "The capsule color challenge": https://www.capsugel.com/knowledge-center/Blogs/capsule-color-challenge. ONdrugDelivery, "Navigating the transition, alternatives to TiO2 in pharmaceutical formulations": https://ondrugdelivery.com/navigating-the-transition-exploring-alternatives-to-tio2-in-pharmaceutical-formulations/, and "Challenges and achievements of TiO2 replacement in hard capsules" (Qualicaps): https://ondrugdelivery.com/challenges-and-achievements-of-tio2-replacement-in-hard-capsules/.
• Industry study for the EMA. Annex I, Use of titanium dioxide as an excipient in human and veterinary medicines, identification of alternatives, industry feedback, final report February 2024, https://www.ema.europa.eu/en/documents/other/annex-i-use-titanium-dioxide-excipient-human-veterinary-medicines-identification-alternatives-industry-feedback-qwp-experts-ema-questions-final-report-february-2024_en.pdf; EFPIA industry submission February 2024, efpia.eu. IQ Consortium, J. Pharm. Sci. 113(5), 2024, "Titanium dioxide replacement," sciencedirect.com. Palugan et al., Int. J. Pharm. 616, 2022. Felton and Timmins, concerns regarding calcium carbonate as an alternative excipient, March 2025, pharmaexcipients.com.
• Regulation, titanium dioxide. Commission Regulation (EU) 2022/63, https://eur-lex.europa.eu/eli/reg/2022/63/oj; FSAI notice on E171; COT statement on titanium dioxide, August 2024, and February 2025 update, cot.food.gov.uk and https://cot.food.gov.uk/COT%20Evaluations; CMS Law note on GB divergence; 21 CFR 73.575, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.575, and FDA titanium dioxide page; FDA color additive petition CAP 3C0325 status; Health Canada State of the Science 2022; FSANZ review page, updated November 2025, https://www.foodstandards.gov.au/consumer/foodtech/Review-of-titanium-dioxide-as-a-food-additive; Swiss FSVO withdrawal 2022 via tdma.info; Commission Staff Working Document SWD(2025) 244 on titanium dioxide in medicinal products, August 2025, https://health.ec.europa.eu/latest-updates/commission-staff-working-document-use-titanium-dioxide-medicinal-products-2025-08-06_en; RAPS summary.
• Colorants, US. 21 CFR 73.70, 73.100, 73.200, 73.350, 73.450, 73.530, 73.1200, 74 subpart A and B, 80.10, 101.22, 201.20, ecfr.gov (73.100, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.100; 73.200, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.200; 73.350, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.350; 73.530, https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-73/subpart-A/section-73.530). FDA, Summary of color additives for use in the United States; FDA Red No. 3 page (revocation January 2025), https://www.fda.gov/industry/color-additives/fdc-red-no-3; FDA, tracking industry pledges to remove petroleum-based dyes, September 2026; FDA letter to industry on "no artificial colors" claims, 5 February 2026, https://www.fda.gov/food/food-chemical-safety/letter-food-industry-no-artificial-colors-labeling-claims; Federal Register, spirulina extract order February 2026 and Haynes Boone note on the March 2026 stay; HHS release on new natural color approvals, May 2025; Manufacturing Chemist on the 2018 iron oxide listing for supplements.
• Colorants, EU and GB. Regulation (EC) 1333/2008 Annex II consolidated (FSAI), category 17.1 as amended by Regulation 2018/1497 (legislation.gov.uk); FSAI labeling requirements page (Article 24 warning); EFSA statement on the Southampton study, 2008; EMA excipients annex, EMA/CHMP/302620/2017 Rev. 2; Directive 2009/35/EC.
• Natural colorants and light fastness. MDPI Colorants 5(3):27, 2026, review of natural colorant stability; Binmei, light stability data: https://www.binmei-color.com/technical-center/light-stability/; Food Processing on replacements for banned colors; Lyfe Group blog, pigments and dyes for capsules: https://blog.lyfegroup.com/pigments-and-dyes-for-capsules-choose-the-right-color; Capsuline blog, capsules with natural colorants: https://capsuline.com/blogs/empty-capsules/all-about-capsules-with-natural-colorants; IACM iron oxide profile.
• Light protection. Int. J. Pharm. 103(1), 1994, iron oxide photoprotection in tablets; J. Pharm. Sci. 2025 film coating photoprotection study; USP <671> revision bulletin.
• Pantone, minimums, two-tone, and printing. Lyfe Group, the art of hard capsule colorization: https://blog.lyfegroup.com/color-capsule-the-art-of-hard-capsule-colorization, capsule colors: https://lyfegroup.com/capsule-colors/, and capsule printing: https://lyfegroup.com/capsule-printing/; Capsugel, Colorista page: https://www.capsugel.com/pharmaceutical-solutions/hard-empty-capsules/colorista-capsules, and Coni-Snap brochure (copy on euromar.co.il): https://euromar.co.il/wp-content/uploads/2021/01/ConiSnap_brochure_full.pdf; Capsuline, FAQ: https://capsuline.com/pages/faqs-capsuline, custom capsules: https://capsuline.com/pages/custom-capsules, colored capsules: https://capsuline.com/collections/colored-capsules, and TiO2-free product page: https://capsuline.com/products/titanium-dioxide-tio2-free-colored-empty-gelatin-capsules-size-00-box-of-75-000; Capsule Depot, custom capsule service: https://capsuledepot.com/pages/capsule-depot-custom-capsule-service; Anxine, empty capsules: https://www.anxine.com/empty-capsules, and color guide: https://www.anxine.com/resources/how-to-pick-the-right-capsule-color; Superior Supplement Manufacturing, custom capsule manufacturing: https://www.superiorsupplementmfg.com/custom-capsule-manufacturing/; Made-in-China listing, Wenzhou Urban Machinery, size 00 custom capsules: https://urbanpackline.en.made-in-china.com/product/SajUcYixOQVk/China-Empty-Capsule-Size-00-Customized-Printed-Empty-Capsules.html; PureCaps USA (capsulesupplies.com), two-tone listing: https://capsulesupplies.com/products/size-00-separated-two-toned-gelatin-capsules; Lonza in-stock color program (FoodNavigator, 2008): https://www.foodnavigator.com/Article/2008/05/20/capsugel-program-allows-fast-access-to-colored-capsules/, and Americas in-stock color brochure: https://dam.lonza.com/dmm3bwsv3/assetstream.aspx?assetid=23590&mediaformatid=10061&destinationid=10016&cat=CHI; Qualicaps, Quali-V product page (printing): https://en.qualicaps.co.jp/product/capsule/quali-v/; Colorcon, Opacode brochure 2025: https://www.colorcon.com/hubfs/Colorcon_Opacode_Brochure_2025.pdf; Ackley Hartnett, types of edible ink: https://ackleyhartnett.com/types-of-edible-ink/; Plastics Decorating, simulating Pantone colors on colored substrates, 2019; Colorcon, Opadry TF poster 2021 (delta E rule): https://www.colorcon.com/hubfs/PDFs%20Pharma%20downloads/Colorcon_OpadryTF_Poster_2021.pdf.
• Perception and differentiation. de Craen et al., BMJ 1996;313:1624, https://www.bmj.com/content/313/7072/1624; Pharmacy 2022;10(4):82; FDA guidance, Safety Considerations for Product Design to Minimize Medication Errors, 2016, https://www.fda.gov/files/drugs/published/Safety-Considerations-for-Product-Design-to-Minimize-Medication-Errors-Guidance-for-Industry.pdf; FDA MAPP 5016.6, https://www.fda.gov/media/99625/download; FDA draft guidance, Replacing Color Additives in Approved or Marketed Drug Products, May 2025 (draft, not final), https://www.fda.gov/regulatory-information/search-fda-guidance-documents/replacing-color-additives-approved-or-marketed-drug-products; Drug Development and Delivery on over-encapsulation shells.

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