I'm not joking
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The whites are not really yellow but an off white. I thought they improved the screen on the iPhone 5 but the screen on my iPhone 4 is much better
Jeez...he was being sarcastic.
I also got one with a yellow tint. some sources online seem to claim that it is due to the glue used, and that it will cure over time and get better. Some claim otherwise (different panels by different makers).
Whatever the truth is, I have noticed that my screen looks bluer now (it took about a week for a minor change, and it has been 2-3 now and I can see that it is very blue).
However, I can't rule out the placebo effect or different lighting conditions. Whatever the case is, it looks fine to me now.
I also went to compare with models in the store (10-15) and while mine does look more "yellow" I noticed ALL the units in the store had a red tint to their screens. Between the two, I would rather have my yellow screen.