The L∗C∗h color space
The L∗C∗h color space
uses the same diagram as the L∗a∗b∗ color space, but uses cylindrical coordinates instead of rectangular coordinates. In this color space, L∗ indicates lightness and is the same as the L∗ of the L∗a∗b∗ color space, C∗ is chroma, and h is the hue angle. The value of chroma C∗ is 0 at the center and increases according to the distance from the center.
Hue angle h is defined as starting at the +a∗ axis and is expressed in degrees; 0o would be +a∗ (red), 90o would be +b∗ (yellow), 180o would be -a∗ (green), and 270o would b∗ (blue).