It is a CALIBRATION issue.
I just hope Apple has a universal calibration.
I cannot believe Apple still hasn't included a display calibrator. It will save them thousands from people who return their phone 1 million times for this "issue".
The calibration issue, if you insist on calling it that, was with the previous models which had displays which were too blue. People get used to that being "correct" and then perceive the iPhone 5 and iPad 3rd Gen as too yellow. Get somebody to measure the white temperature and you'll find it's pretty much 6500K, the standard colour temperature reference for white.