Some clarification on Data's uniform colors:
The switching of red and yellow from their TOS roles was already planned from the beginning.
The problem was that Data tested bad in blue. He was originally supposed to be called the science officer, just like Spock. However, when they put him in the blue medical/sciences uniform, they didn't think it worked well with his android makeup and contact lenses. So they created a new position, operations officer, that allowed him to wear the yellow ship operations uniforms. Red was never really a consideration for him.
It's too bad, though. Personally, I think his makeup and contacts look horrible with the yellow and would have looked ten times better in either red or blue. As I recall, there were even some Photoshopped images posted around here a while back showing him in the different colors.