White

White is the combination of all the color of the visible light spectrum. White is an achromatic color, since it has no hue. The impression of white light can be created by mixing appropriate intensities of the primary color of light — red, green and blue — a process called additive mixing, but the illumination provided by this technique has significant differences from that produced by incandescence. In nature, white results when transparent fiber, particle, or droplet are in a transparent matrix of a substantially different refractive index. Examples include classic "white" substances such as sugar, foam, pure sand or snow, cotton, clouds, and milk. Crystal boundaries and imperfections can also make otherwise transparent materials white, as in the milky quartz or the microcrystalline structure of a seashell. This is also true for artificial paints and pigments, where white results when finely divided transparent material of a high refractive index is suspended in a contrasting... full article at wikipedia