Apple.
I've on my 4th one already.
First went from 13" to 15" and all 3 have had part of the screen tinted yellow. The 13" was fine. It was a newer build and the 15" have all been Jan/Feb builds.
So I think I am going to order online and try my luck on a newer manufactured unit, then return this one to the apple store. I originally bought on Monday the 15th. I exchanged for this newest one yesterday.