Using GIMP: Correcting and Touching Up Your Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 126

Figure 2.53
Solarizing an image by
corresponding settings
in the gradation curve.
2.5.10 Adjusting Hue and Saturation
Have a look at your miami-impro image with the Hue-Saturation function
open ( Colors > Hue-Saturation ). What could you do with it?
Let's see: The sky over the houses is cyan and turquoise. Move the Hue
slider slowly to the right and observe how the color of the sky changes. It
slowly changes to blue, but the other colors in the image also change with it.
The Master button is the default setting for the Select Primary Color to Adjust
function, so all primary colors are selected. When you move the slider, all
colors in the image are rendered.
Suppose you want to change the color of the sky from cyan to sky blue. To
do so, check the C button for cyan in the Select Primary Color to Adjust section.
Now if you move the Hue slider, you will be changing only colors in the cyan
color range. Move the slider to the right until the sky (and all other blue tones
in the image) becomes more of a sky blue. The sky can be brightened up at the
same time by moving the Lightness slider to the right.
The image now looks better, but you haven't confirmed the changes
by clicking OK yet, so you can continue. What about the color intensity and
saturation? I like my images to have intense colors. To see the effect, increase
the saturation in the image by moving the Saturation slider to the right. But
first you must click the Master button to process all primary colors. Try reducing
the saturation by moving the slider to the left. This changes the image to a