My screen is a little yellowish compared to my iPad. So what? It works fine and the colors are amazing.
I'm not denying that it's an issue. White should be white, not yellow. If you don't like it just ask for a replacement. It's your right and no one could argue with that.
For me, I wont be able wait another 2 weeks for a replacement after waiting 3 weeks for my current one. A replacement could have a much worst problem like an interlacing screen, a problem with touch ID, or that battery issue. It's a lottery.