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
Aircraft camouflage 15mph (25kph) compared to glossy black, which, being smoother, produced less drag. Since, however, black camouflage made the planes conspicuous on moonlit nights and against cloud, a variation of a day camouflage scheme was eventually chosen. In the early years of World War II, German U-boats often escaped attack by aircraft because they spotted the aircraft while it was still far away as a black dot in the sky, no matter what camouflage colors were used. To solve this problem, in 1943 the U.S. Navy, following the Canadian diffused lighting camouflage trials on warships, conducted secret experiments on counter-illumination in