In this case, I threw a cyan cast on the lower half of the image by selecting it and then pulling
down the curve of the red channel only, cyan being the complement of red. This is just to illustrate
the point that color cast can be added or removed and white balance corrected by making adjustments
in each of the RGB channels, usually by leaving each channel's curve linear and moving the White and
Black Points to the extremes of the histogram graph.

When I get time I'll do a better illustration of this.

Click 'next' to continue.