Color correction is used to eliminate the overlap in the color channels caused by the fact that the light intended to be detected only by pixels of a certain color is partially seen by pixels of other colors. For example, the red light is partially seen by green and blue elements of the CCD. A properly adjusted color correction matrix can eliminate this overlap.
In order for the white balance to work properly, the sum of each row in the color correct matrix (i.e. rr+rg+rb) should be equal to 1.