I think I have figured out what's causing this "discoloration." It's not the video card. I tried both with 9400 and 9600, both are having same issues.
The problem is the display and it's the heat that's causing this.
All displays/monitors are suppose to get hot. Since LED Cinema Display is much brighter and color heavy than other monitors, I can understand that it generates heat. Do you notice that their is a small fan that's blowing hot air out of the display? Or am I just feeling the excessive heat? (Check lower left side of the display, under the left side of the speaker)
When I connect the LED Cinema Display to the MacBook Pro, I don't see any problems with the display. Even working for a few hours I don't see it. But this afternoon. I noticed the discoloration, color shift on my screen. So I touched the lower left part of the display and it was very hot. If I had to exaggerate a little, I could get burnt.
It could be just my display that's defective, or it might be a design flaw. But then again, what do I know, I'm not an Apple designer.
I'm gonna give the Apple support a call tomorrow and see if there's any known issues regarding this.