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
Dazzle camouflage the Animal Kingdom". Seeing the opportunity to put his theory into service, Thayer wrote to Churchill in February 1915, proposing to camouflage submarines by countershading them like fish such as mackerel, and advocating painting ships white to make them invisible. His ideas were considered by the Admiralty, but rejected along with Kerr's proposals as being "freak methods of painting ships ... of academic interest but not of practical advantage". The Admiralty noted that the required camouflage would vary depending on the light, the changing colours of sea and sky, the time of day, and the angle of the sun. Thayer