Chameleon turquoise, and purple. Chameleon skin has a superficial layer which contains pigments, and under the layer are cells with guanine crystals. Chameleons change colour by changing the space between the guanine crystals, which changes the wavelength of light reflected off the crystals which changes the colour of the skin. Colour change in chameleons has functions in camouflage, but most commonly in social signaling and in reactions to temperature and other conditions. The relative importance of these functions varies with the circumstances, as well as the species. Colour change signals a chameleon's physiological condition and intentions to other chameleons. Chameleons tend
Snow camouflage to escape the conclusion that cryptic brown summer plumage becomes a liability in snow, and white plumage is therefore another cryptic adaptation." All the same, he notes, "in spite of winter plumage, many Ptarmigan in NE Iceland are killed by Gyrfalcons throughout the winter." Some animals of the far north, like the showshoe and Arctic hares, Arctic fox, stoat, and rock ptarmigan change their coat colour (by moulting and growing new fur or feathers) from brown or grey summer camouflage to white in the winter; the Arctic fox is the only species in the dog family to do so. However,