This software allows you normalize the response curves for red, green, and blue. it does this perfectly so long as you know what you are doing (hint: blur your eyes a bit when trying to equalize top and bottom halves). Unfortunately, you're still on your own for selecting the correct white balance. You need some kind of hardware colour reader to really get it perfect. The interface is a bit difficult to use at first.

This is one of the first things I run on a mac. It's not just for graphics designers by the way. I'm a slightly colorblind unix guy and I really notice the improvement.