Adjusting the Colors
In common with other image editing programs, GIMP has options for adjusting the colors in a photo. You can find all these options in the Colours menu at the top of the screen. If your picture has a tint of color you don’t want, or if you would like to add a tint, use the Colour Balance settings to alter the amount of red, green, and blue in the image. The Brightness and Contrast settings can help to bring out detail in shadows, or to give the image more impact.
There are also options in this menu (further down, under Auto) to automatically adjust the colors using six different methods. These can give strange and undesirable results, but you can always undo them with Ctrl+Z if you don’t like them. The Normalize option can be a quick fix for images that look a bit wishy-washy, and the White Balance option can fix pictures that don’t already have strong black and white areas.