Last spring, my niece and I made a trip to a home improvement store to put together a Mother’s Day planter for my sister. My niece had a clear vision: my sister’s favorite color is blue, so we were going to buy blue flowers. We walked every aisle of the garden center. We checked the annuals, the perennials, and the hanging baskets then left with purple, red, and a grumpy 7-year-old.
It turns out we were not up against a bad selection. We were up against biology.
The Problem with Blue
Blue is one of the rarest colors in the natural world. The food industry is currently finding that out the hard way. There is a good chance you have eaten something blue today. Maybe it was the frosting on a birthday cake, the coating on some M&M’s® candies, or the sports drink in your refrigerator. That blue almost certainly came from a petroleum-based synthetic dye, and for the first time in decades, the food industry is being asked to find something better.
The FDA banned Red Dye No. 3 in January 2025, and pressure has been building around the remaining synthetic dyes ever since, including Blue No. 1 and Blue No. 2. Major food brands have begun announcing plans to reformulate.
There is just one problem. Blue is genuinely, stubbornly hard to make in nature. It turns out that blue has almost nothing to do with color, and almost everything to do with light.
The Illusion of Blue
You already know the sky isn’t really blue. Neither is the ocean. What is surprising is how much company they have. We’ve been drawing beautiful days with a blue crayon our whole lives, but almost none of that blue was ever really there. It was light behaving in ways our eyes interpret as blue. The natural world appears full of blue, but not much of it actually exists.
Animals that appear blue, from bluebirds to Morpho butterflies, don’t contain a single blue pigment. The Morpho butterfly, whose wings shimmer with an almost impossibly saturated blue, exists entirely as a trick of light. If you ground up those wings into powder, you would get something brown or gray. The blue is not pigment; it is physics. The wings are covered in nanoscale structures arranged with such precision that they reflect only the wavelength of light our eyes register as blue. The butterfly is not producing color. It is manipulating light.
This phenomenon is called structural color, and it’s not just a clever workaround. It is purposeful. Male Morpho butterflies use that flashing iridescence for mate attraction and territorial signaling. The way the color shifts and shimmers as they move makes it eye-catching and hard to fake. Even the blue of a robin egg serves a light-related purpose. The pigment responsible for that color absorbs UV radiation, essentially acting as a built-in sunscreen for the embryo developing inside. Structural blue isn’t decoration. It is a relationship with light.
Light Seeks Blue
There is a reason light keeps making blue, even when biology cannot. Blue light has a short wavelength, which means it interacts with very small things in ways that longer wavelengths of red and yellow simply do not. The sky scatters it. Nanoscale structures on a butterfly wing bend it. Air molecules, water, chitin (the material in butterfly wings): all of them redirect blue while red and yellow pass through. The mechanism changes, but the physics does not.
Blue is not everywhere in the living world, though, because light being present is not enough. The sky and ocean are blue through physics alone, at no biological cost. For living things, producing blue, whether structurally or chemically, requires a very specific and energy-demanding relationship with light. Most never develop that relationship because their survival doesn’t require it.
The organisms that do tend to share something in common: interacting with light is already central to what they do. Cyanobacteria and algae produce phycocyanin to capture light for photosynthesis. The blue pigment in robin eggs comes from the breakdown of hemoglobin, a molecule whose whole job is moving the oxygen that makes energy from light possible. In nature, blue pigment is almost always a byproduct of doing something with light. The organisms that cracked it weren’t trying to be blue. They were trying to use light, and blue came along for the ride.
Blue Without a Purpose
Indigo is something of an exception among natural blues. Unlike phycocyanin or biliverdin, it didn’t evolve in service of light. It has no photosynthetic role, no protective function. It just happens to have a molecular structure stable enough to hold its color under real-world conditions. That stability made it valuable as a dye for thousands of years, and it is what the food industry was chasing when it reached for a petroleum-based version of the same molecule. Blue No. 2, one of the dyes now under regulatory scrutiny, is synthetic indigo. The result looks the same to your eyes. The resemblance ends there.
The concerns driving the current regulatory pressure, potential links to behavioral issues in children and cancer risks in animal studies, are real. These molecules were engineered purely for appearance, with no biological roots and no relationship to the reason blue exists in nature at all.
The food industry reached for a shortcut, and for decades it worked. With regulatory pressure mounting and consumers demanding cleaner labels, that shortcut is being reconsidered. Now it is back where it should have started: biology.
Back to Biology
If you want to find blue in nature, look for where light matters most. The shrimp glowing in the dark. The algae harvesting light at the surface. The butterfly advertising itself in motion. Blue is not a color that exists in stillness.
So where does that leave the food industry? Looking to algae, as it turns out.
A team of researchers at Cornell University published a study in July 2025 in the journal Food Hydrocolloids with a promising answer: phycocyanin, the blue pigment protein found in spirulina algae, already used in limited quantities to give “natural blue” M&M’s® candies their color. The problem is that phycocyanin evolved to work with light, not sit on a grocery shelf. That molecular sensitivity makes it vulnerable to breaking down under heat and light during food processing and storage.
A molecule built for a life in the water does not automatically translate to a life in a bag of snacks. The Cornell team’s solution was to go deeper into the protein’s structure, breaking it down to its molecular building blocks and reassembling it into smaller, more uniform particles that are more stable and more functional. “It’s like using a magnifying glass to see and understand changes in protein structure,” said Alireza Abbaspourrad, the study’s corresponding author.
What the Cornell research represents is a return to blue that actually means something, working with a molecule that earned its color through a deep and ancient relationship with light. We have taken the same approach with some of our best-known research tools on exactly this idea. NanoLuc, one of the most widely used bioluminescent reporters in life science research, was developed from a protein found in a deep-sea shrimp that produces blue bioluminescent light in luminous clouds as a defense against predators. Our scientists understood its structure and through careful engineering turned it into a research tool sensitive enough to detect activity inside a single living cell. The shrimp never knew it was carrying something so useful. It was just trying to survive in the dark.
Blue has always been a kind of paradox: the color that floods the sky and fills the ocean, built from nothing more than the way light moves through very small things. Nature figured that out long ago. Scientists are still working on the frosting.
Sources
- Li Q, Huang Q, Abbaspourrad A. Elucidating structure-functionality relationships of phycocyanin through size-exclusion chromatography coupled with in-line small-angle X-ray scattering. Food Hydrocolloids. 2025. DOI: 10.1016/j.foodhyd.2025.111798
- U.S. Food and Drug Administration. FDA Revokes Authorization for Use of FD&C Red No. 3 in Food and Ingested Drugs. January 15, 2025. https://www.fda.gov/food/hfp-constituent-updates/fda-revoke-authorization-use-red-no-3-food-and-ingested-drugs
- Hall MP, Unch J, Binkowski BF, et al. Engineered Luciferase Reporter from a Deep Sea Shrimp Utilizing a Novel Imidazopyrazinone Substrate. ACS Chemical Biology. 7(11):1848-1857. 2012. DOI: 10.1021/cb3002478
- California Office of Environmental Health Hazard Assessment. Potential Impacts of Synthetic Food Dyes on Activity and Attention in Children. May 2025. https://publichealth.berkeley.edu/articles/spotlight/research/new-report-shows-artificial-food-coloring-causes-hyperactivity-in-some-kids
Elise Johnson
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