This is an old post i did stumbling upon.
If i do understand Chris correctly the main problem is color casting due to mixed types of light sources.
I have found away that very easily removes those cast. As you can see i managed to remove the cast successfully. Though Chris did manage to keep the yellows in the back of the church which i do like. (this could also be achieved on this image to delete parts of the layer in that area.) The way i did it also there the cast got removed.
It looks or i did desaturate though that is not true.
I do this all in LAB (in this image i did also play a bit with masks and overlay's, though that is not relevant to the cast problem)
The method is as simple as effective:
Set a marker at the where the cast is visible. The A and B values should be zero there.
move the center of the A and or B channel curve to the crosshair until the value is zero. Well the cast is now fixed though we did created a new one by moving the center. All we have to do is to restore the center. So we pick a point right above the center (in B channel moves) and move that to the center until also that value is zero and all casts are fixed.
I happen to use an open source tool (can't afford PS and CM) hope that does not matter.
More about this way can be found at:
Discussing with Lee Varis:
http://blog.varis.com/2011/10/17/simple-fix-for-mixed-lighting-problems/
how to's and examples:
http://www.flickr.com/groups/delaboratory-users/discuss/72157627878741061/
http://www.flickr.com/groups/delaboratory-users/discuss/72157627970443017/
http://www.flickr.com/groups/delaboratory-users/discuss/72157627925900509/