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
Active camouflage It uses about 1000 hexagonal Peltier panels to cover the sides of a tank. The panels are rapidly heated and cooled to match either the temperature of the vehicle's surroundings, or one of the objects in the thermal cloaking system's "library" such as a truck, car or large rock. Active camouflage is used in several groups of animals including cephalopod molluscs, fish, and reptiles. There are two mechanisms of active camouflage in animals: Counterillumination camouflage, and color change. Counterillumination is camouflage using the production of light to blend in against a lit background. In the sea, light comes down from