Using GIMP: Correcting and Touching Up Your Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 127

grayscale image. Choose a saturation level to your liking. If something goes
wrong, you can set the slider back to its default position. If you want to discard
all changes and start anew, you can click on the Reset button.
Confirm the settings in the window by clicking the OK button, and then
save your image. IF you don't want to save your image under a new name,
simply click the Cancel button. The changes will be discarded and the image
will return to its original state.
Figure 2. 54
The Hue-Saturation
window with the
settings to change
the hue for cyan
Figure 2.55
The miami-impro image before and after the color correction. The rendered hue of the sky is seen at the top left. Colors have
been intensified by increasing the saturation.