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 smaller shapes with dithering; this softens the edges of the large scale pattern, making the underlying objects harder to discern. Pixellated shapes pre-date computer aided design by many years, already being used in Soviet Union experiments with camouflage patterns, such as "TTsMKK" developed in 1944 or 1945. In the 1970s, US Army officer Timothy R. O'Neill suggested that patterns consisting of square blocks of colour would provide effective camouflage. By 2000, O'Neill's idea was combined with patterns like the German "Flecktarn" to create pixellated patterns such as CADPAT and MARPAT. Battledress in digital camouflage patterns was first designed by the