How Does a Chameleon Change Color Without Repainting Its Skin?

A chameleon does not change color simply by moving bags of pigment around its skin. In some species, much of the transformation comes from rearranging structures smaller than the wavelength of visible light.

Panther chameleons possess specialized skin cells called iridophores. Inside these cells are tiny crystals made from guanine, a substance also found in genetic material. The crystals form organized arrays that interact with light.

When the crystals sit close together, the array reflects shorter wavelengths. When the chameleon becomes excited and the spacing expands, it reflects progressively longer wavelengths. A relaxed green area can therefore shift toward yellow or orange as the crystal arrangement changes.

Pigments in other skin layers combine with this reflected light. Blue light returning through yellow pigment, for example, can create the green appearance seen by an observer. Dark pigment cells also influence brightness and pattern.

Chameleons change color for several reasons. Communication is particularly important. A male confronting a rival may display bright, rapidly changing colors, while courtship, stress, temperature, and light can produce different responses. Camouflage matters, but the popular image of a chameleon perfectly copying any background exaggerates what most species can do.

Researchers have also found a deeper layer of more irregular crystals that reflects a substantial amount of infrared radiation. This may help protect the animal from excessive solar heating.

The visible change is therefore not comparable to spreading fresh paint across the body. The chameleon alters the spacing inside a living photonic structure, changing which parts of ordinary light are returned to the world.