Blue, the phantom colour of the natural world

Blue is everywhere—hovering above us in the sky, stretching across the oceans, and permeating the symbols of royalty, peace, and beauty. And yet, in the natural world of plants and animals, the colour blue is astonishingly rare. Despite its visual dominance in our everyday surroundings, fewer than 10% of plant species bear blue flowers, and even fewer animals appear blue. So why is such a beloved and seemingly omnipresent colour so elusive in nature?

No true blue pigment in nature

The scarcity of blue in nature begins at the molecular level: there is no true blue pigment that is common or stable in living organisms. Unlike red, yellow, or green—colours that are produced by straightforward pigments—blue is more of an optical illusion, a trick of physics rather than chemistry.

In the plant kingdom, blue tones are usually the result of pigment modification. Most commonly, plants rely on red pigments called anthocyanins. By altering the pH levels within plant tissues and combining with other molecules, these pigments can be manipulated to reflect blue light. This is how we get the enchanting blues of hydrangeas, delphiniums, cornflowers, and morning glories. However, achieving this effect is chemically complex and energetically expensive, making true blue blooms a botanical rarity.

Even rarer are blue leaves. While a few rainforest plants have evolved bluish foliage, the physics of light absorption explain why this is uncommon. Blue light carries more energy than other colours in the visible spectrum. Plants absorb blue light efficiently for photosynthesis, so reflecting it—by appearing blue—means losing out on this crucial energy source. Green chlorophyll remains dominant because it reflects less energetic green light, allowing plants to maximize their energy intake.

Please also read: The strange and sinister world of parasitic plants

Animals and the art of light manipulation

Animals face an even more intricate challenge. Many animal pigments are diet-derived—like flamingos turning pink from shrimp or goldfish shimmering golden from carotenoids in their food. But since no plants produce a true blue pigment, animals can’t eat their way to blue.

Instead, nature turns to physics once again: structural coloration. This phenomenon uses microscopic physical structures to scatter and reflect only blue wavelengths of light. The stunning blue of a morpho butterfly’s wings, for example, comes not from dye, but from nanostructured scales that bend light in a specific way. Change the shape of those scales, and the colour disappears.

Similarly, blue feathers in birds—such as blue jays or the indigo bunting—are the result of microscopic air pockets and keratin layers that scatter light. Think of it like noise-cancelling headphones, but for light: all wavelengths are cancelled out except for blue. In fact, if you were to crush a blue feather, it would turn grey or black—because the structural coloration would be destroyed, revealing there’s no blue pigment at all.

Only a few animals, like the obrina olivewing butterfly, are known to produce true blue pigments—and even then, the chemistry behind this rare feat is still being studied.

The evolutionary edge of being blue

If creating blue is so difficult, why bother at all? Because in nature, rarity can be power.

For plants, producing a blue flower may attract a unique set of pollinators. Bees, for instance, are particularly sensitive to blue and violet wavelengths, which may explain why some flowers evolved to reflect them. The diversity of flower colours seen today is, in part, the result of pollinator preferences shaping floral evolution over millions of years.

In animals, blue is often used to make a statement—either to attract mates or to warn off predators. Male birds of paradise perform elaborate mating dances clad in shimmering blue plumage. Poison dart frogs flaunt their electric-blue skin to advertise toxicity. These vivid blues, while rare and energetically costly, can be evolutionary advantages in the arms race of survival and reproduction.

Our fascination with blue

The human attraction to blue runs deep. Surveys consistently show that blue is the favourite colour across cultures worldwide. Historically, blue was also one of the most difficult colours to produce artificially. Ancient civilizations prized Egyptian blue—made from calcium copper silicate—but the technique was lost for centuries. Until synthetic dyes were invented, blue remained expensive and exclusive, reserved for the garments of royalty and the divine.

Even today, the pursuit of the perfect natural blue continues. Horticulturists have long attempted to create a true blue rose, with limited success. However, in a groundbreaking achievement, Japanese scientists recently bred the first genetically engineered blue chrysanthemum by combining genes from blue-producing plants and manipulating pigment pathways.

Conclusion

In a world bursting with green forests, red berries, and golden sunsets, blue remains a visual anomaly—an optical enchantment that reminds us how complex and creative nature can be. Whether it’s the iridescent wing of a butterfly, the delicate petal of a cornflower, or the flash of feathers in a rainforest canopy, blue never ceases to captivate.

Its rarity is not a limitation but a feature—an evolutionary badge of distinction and a beacon of beauty that transcends biology. Blue is the colour of the extraordinary.