HLS Colour Model:

This model has the double-cone representation illustrated in Figure. The three colour parameters in this model are called as hue (H), lightness (L), and Saturation (S).

Hue has the similar meaning like in the HSV model. This specifies an angle around the vertical axis that locates a chosen hue. In this model, H = 00 corresponds to blue. The remaining colours are specified around the perimeter of the cone in the similar order as in the HSV model. Magenta is at 60°, red is at 120°, and cyan is situated at H = 180°. Again, complementary colours are 180° apart on the double cone.

The vertical axis in this model is called as lightness, L. At L = 0, we have black, and white is at L = 1. Gray scale is along with the L axis, and the "pure hues" lie on the L = 0.5 plane. Saturation parameter S again specifies relative purity of a colour. This parameter varies from 0 to 1, and pure hues are those for which S = 1 and L = 0.5. As S reduces, the hues are said to be less pure. At S = 0, we have the gray scale.

As in the HSV model, the HLS system permits a user to think in terms of making a selected hue darker or lighter. A hue is selected with hue angle H, and the desired shade, tint, or tone is obtained by adjusting L and S. Colours are made lighter by increasing L and made darker by decreasing L. While S is decreased, the colours move toward gray.