1. Removing Color Casts in GIMP
By: Chesney and Derrick

2. What is a Color Cast
A color cast occurs when the Red, Green, and Blue channels of an image are not properly balanced. The cast can be across the entire range of pixel values or can limit itself to the highlight, shadow, or mid-tones of the image. Color casts are common in photographs. They occur because, under certain circumstances, the sensitivity of film to color is different than the sensitivity of the human eye.

3. When do I remove Color Cast
As stated before,We get color casts, when we take photos in different environments with various lighting conditions. For example, we get blue color cast when photographing outdoors, we get a pale sickly yellow playing throughout pictures captured indoors under electrical lighting and so on.
There are many methods used to eliminate color casts, one of the easiest being the manipulation of the color balance.

4. How do I do this?
In GIMP, apply Colors > Auto > White Balance from the main menu. This should automatically remove color casts from most photos. Usually, the brightness and contrast are enhanced as well. To make the colors look richer, apply Colors > Auto > Color Enhance to make the colors more saturated.

5. If that doesn’t fix it, you can manually attempt to do so using the adjust color balance tool, starting with highlights and then moving to the other options until the required balance is found
Moving a slider towards the color on one end will increase the intensity of that color in the photo and reduce the intensity of the color on the other end of the slider.

7. What do all of the options do