Saturation thus describes the impression of the colorfulness of a surface in relation to its brightness: saturation = color/brightness. Unsaturated colors are achromatic colors ( black, gray, white). Colors with low saturation are called pastel colors. Saturated colors are characterized by high spectral purity and high color intensity. In the color wheel, saturation is indicated by the length of the color vector from the central axis.
The human eye can distinguish about 130 different color saturations.