Color

I prefer to use HSV color space instead of RGB because they better match how people perceive color. The HSV color space consist of three components: hue, saturation and value.

• Hue: The basic color in the color wheel, ranging from 0 to 360 degrees where both 0 and 360 degrees are red.
• Saturation: How pure (vs. dull) the color is, ranging from 0 to 100, where 100 is fully saturated and 0 is gray.
• Value: How bright the color is, ranging from 0 to 100, where 100 is as bright as possible and 0 is as dark as possible (black).

An example where color's value reduced by 20 (100, 80, 60):

See also this article in msdn to get more details.