For that matter, why is anything any color at all? In the last Science Theatre column on why snow is white, we said that the light we see things with from the sun, from our light bulbs is called white light and can be broken down into the colors in the rainbow in order of their wavelengths.
The snow is white because all the colors are reflected and refracted equally without any color range dominating.
This is not so when white light hits objects which we donít see as white or gray.
Most objects tend to reflect only some of the light falling on them. The light contains all of the colors, but the objects reflects selected colors and absorbs the rest.
This is called "subtractive color mixing" because some of the colors are subtracted out of the light.
Grass appears green because all of the colors in the rainbow are absorbed into the leaves of the grass except green.