I remember an apple store person talking about this issue, actually. I'm almost positive he told me that the color shift was a bi-product of the glossy screens (not to mention viewing angle). Honeslty, I don't know if that's where the problem stems, but it's lit from the bottom, so I assume this is normal.
Honestly, I would take it to the apple store to compare it to other macbooks if possible. If it looks like the others do, then you don't have a valid complaint.