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
Military camouflage Aircraft camouflage faces the challenge that an aircraft's background varies widely, according to whether the observer is above or below the aircraft, and with the background, e.g. farmland or desert. Aircraft camouflage schemes have often consisted of a light colour underneath and darker colours above. Other camouflage schemes acknowledge that aircraft may be seen at any angle and against any background while in combat, so aircraft are painted all over with a disruptive pattern or a neutral colour such as gray. Second World War maritime patrol aircraft such as the Consolidated PBY Catalina flying boat were painted white, as aircraft