The Grain and Noise drawing modes

The Grain mode adds a multi-colored grain to the current image. This creates a texture imitating a light photographic grain.
The Noise mode adds a single-colored grain. The color applied is the A color.

The Grain and Noise modes themselves also depend strongly on the power and opacity of the drawing tool. Here the A color is a gray color.

Penbrush tool in Grain modePenbrush tool in Noise mode