How does a panther chameleon change colour?

In the zoo's reptile house, Cú Bông stopped by a bright green panther chameleon lying still on a branch. It was so still that at first Cú Bông took it for a leaf.

Cú Bông guessed that chameleons change colour only to hide. Just then, another male chameleon crept along the same branch.

The green chameleon slowly turned yellow, then orange, with patches of red. Among the green leaves, it stood right out. So why change colour this time?

A panther chameleon's skin has a layer of cells holding tiny crystals in a neat lattice. When the animal is calm, the crystals sit close together and reflect blue light. Researchers explain that this blue, with yellow pigment in the skin, gives the green we see.

When a male displays to a rival, the space between the crystals can widen. As they spread apart, the light they reflect shifts from blue towards yellow, orange or red. The male turns yellow, orange or even red, and stands out to his rival.

Move the slider to spread the crystals, then look at the colour model under the picture. This is a simplified model, magnified many times.

In panther chameleons, light reflected by a crystal layer in the skin, with yellow pigment, gives the colour we see. When a male displays to a rival, his crystals can spread apart and he can turn yellow, orange or red.