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 with magnetic sensors. Horizontal coils around the whole or parts of the ship generate magnetic fields to "cancel out" distortions to the earth's magnetic field created by the ship. Ship camouflage was occasionally used in ancient times. Vegetius wrote in the 4th century that "Venetian blue" (bluish-green, like the sea) was used for camouflage in the years 56–54 BC during the Gallic Wars, when Julius Caesar sent his scout ships to gather intelligence along the coast of Britain. The bluish-green scout ships carried sailors and marines dressed in the same colour. The emphasis on hand-to-hand combat, and the short range