It's the temperature of the screen. Apple has gradually moved from bluer colors 2G iPhone and 1G iPod Touch to the current lineup that has a warmer yellow-ish tint.
Look here https://forums.macrumors.com/threads/726743/
Mine looks exactly the same as my 3G. These tints are gradually yellower from side to side. I think it's a defect.
If you click check for update there is a new update that fixes this problem and makes the screen look normal again.
I moved from the original iPhone to 3G S and the screen is just as nice or nicer. Pics appear a bit warmer but I'm not seeing any yellow tint (at least in whites).
Original Poster, Get used to it,
this is no longer a boutique item, welcome to mass-production, lowest common denominator, ect, things we use to attribute to Microsoft....
8 is the new 10...
If you click check for update there is a new update that fixes this problem and makes the screen look normal again.