The Saturate and Unsaturate drawing modes

These two modes are used to increase or decrease pixel saturation.
A highly saturated color is a very bright color whereas a less saturated color is rather dull and closer to gray. Here, the Pen Brush tool was used with an opacity and power of 100% for a radius of 30 pixels.

Pen Brush tool in Saturate modePen Brush tool in Unsaturate mode

The Saturate mode will increase the parasol's red pixels components and render them more vivid.
The Unsaturate mode will render them totally gray.