Three Components of Color

As we now know all perceived colors can be represented by three independent variables, either the LMS responses, or the tristimulus values under the primaries of a given color system, such as RGB or XYZ. In many situations (e.g., computer image processing), it is more convenient to represent a color by a different set of three independent variables HSL (or HSI, HSV). These are defined as

• Hue: the dominant wavelength, the redness of red, greenness of green, etc.
• Saturation: the purity of the color, or how much white is contained in the color. For example, red and royal blue are more saturated than pink and sky blue, respectively.
• Luminance (intensity, value): the intensity of the light.

  Brightness: for measuring self-luminous objects that emits light (CRT, etc.)

  Lightness: for measuring reflected light.

The hue, saturation and luminance can be obtained given the tristimulus values of a color under any color system.