Color or colour is the visual perceptual property corresponding inhumans to the categories called red, blue, yellow, green and others. Color derives from thespectrum of light (distribution of light power versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra. By defining a color space, colors can be identified numerically by their coordinates.
Ref: http://en.wikipedia.org/wiki/Color
