HSB: hue, saturation, and brightness
This scheme provides a device-independent way to describe color.
• Hue is the actual color. It is measured in angular degrees counter-clockwise around the cone starting and ending at red = 0 or 360 (so yellow = 60, green = 120, etc.).
• Saturation is the purity of the color, measured in percent from the center of the cone (0) to the surface (100). At 0% saturation, hue is meaningless.
• Brightness is measured in percent from black (0) to white (100). At 0% brightness, both hue and saturation are meaningless.
Brightness as it is described here refers only to relative values
within a source that we are looking at (for example, a display screen or
printed document). It is also called value or luminance. The distinction
between levels of brightness is actually logarithmic, not linear as
the HSB scale would imply.
The “B” scale of HSB is used to determine the contrast between
two colors, regardless of hue; this is usually called the luminance ratio.
It is important to Web designers, since a ratio of less than 5:1 between text and
background (10:1 for small text) can be very difficult for many people to read.