You can find this filter through
->->.
The Scatter RGB filter adds a normally distributed noise to a layer or a
selection. It uses the RGB color model to produce the noise (noise is
added to red, green and blue values of each pixel). A normal
distribution means, that only slight noise is added to the most pixels
in the affected area, while less pixels are affected by more extreme
values. (If you apply this filter to an image filled with a solid grey
color and then look at its histogram, you will see a classic bell-shaped
Gaussian curve.)
The result is very naturally looking noise.
This filter does not work with indexed images.
