I just picked up a 13" rMBP this evening and upon turning it on, I noticed the 1/3rd of the upper of the screen has a more magenta color tint where the rest of the screen is more green.
Just replaced the unit. The replacement is much better, no issues. Other than... the very edge of the top and bottom is "blue glow" My iPad 3 had this as well. I figure its a common thing with high resolution display