Figure 10.70. The “Color” sub-menu
The Color submenu of the Layers menu contains operations that alter colors within the image. The top entries give access to the Color tools, which are described in the Toolbox chapter.
You can accede to it via Layer->Colors.
In the “Colors” sub-menu you will find:
Section 10.17, “ Desaturate ”
Section 10.18, “ Invert ”
Section 10.19, “ Submenu: Auto ”