I have to mention that I went down the same road you did and in the end I concluded that there has been no color shift. The colors are out of balance, but that is an easy fix. Also, you have to try both ways of removing red. You can’t just assume it is the magenta/green channel that is off. I have found it is not. That is the most solid channel. It is the cyan/red channel and the yellow/blue channel that are both off. It is tempting to shift the colors, but that really just makes the problems worse. If you rebalance the colors you will get a much nicer result.