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
M90 (camouflage) the brown color in the FOA camouflage). Navy blue was chosen instead of black because natural shadows generally tend to be in shades of blue to the human eye. The M90 combat clothing entered service during the late 1980s, with widespread use beginning the early 1990s. It replaced the earlier olive green M59 field uniform. The uniform is available in several different models. The changing missions for the Swedish armed forces, with a heavier emphasis on missions abroad, has led to two new models. M90 (camouflage) M90 camouflage is the camouflage pattern for the uniform system 90, used by the