Color Balance
The Color Balance command lets you adjust the color balance of an image by shifting the colors between complementary pairs of the primary RGB color values and secondary CMY color values.
The dialog for Color Balance adjustment can be called by clicking on "Colors -> Color Balance".
For example, if you want to tone down the red in a photo, you can shift the color values from red to cyan. You can also change the hue values to change the colors used in an image.