Colours (hues) can be detected by many species. The wavelengths in sunlight reaching the surface of the Earth range from ultraviolet (300 nanometers) to above 1000 nanometers in the infrared. The human eye can detect light from about 400 nm (violet) to 800 nm (red). Insects can detect short wavelengths (345 nm). Snakes can detect infrared (heat radiation). The normal human eye uses three pigments with absorptions centered at 420 nm, 534 nm, and 564 nm. All cultures and languages use basic colour terms that correspond very closely with a prototypical midrange of hues; i.e. ‘blue’ is the same blue in every language. There are in all about fifteen specific physical causes of colours. In addition to incandescent sources and pigments, there are colours due to iridescence (interference patterns), refraction (rainbows), scattering (blue sky), and diffraction (opal). Colour printing uses mixtures of cyan, magenta, and yellow. The information that colour gives us is used in a huge variety of adaptations and behaviors in animals and humans. We use colour coding in a huge array of applications including science. For example, the display of information in ‘false colors’ (e.g. temperature on a weather map) is a standard technique in visualization.
