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 observation positions were hand-painted in disruptive patterns by artists known as camoufleurs, and they sometimes varied their patterns seasonally. Uniforms were largely of a single colour, such as the British khaki; but snow camouflage clothes came into use in some armies by 1917. For example, Austro-Hungarian troops on the Italian front used skis and wore snow camouflage smocks and overtrousers over their uniforms, and improvised white cloths over their uniform caps. Several armies in the Second World War in Northern European countries preferred separate winter uniforms rather than oversuits. The Waffen-SS went a step further, developing reversible uniforms with separate