Can you have them open and test your replacement iPhone in the Apple store, to make sure your not just getting another dud? I'd hate to go through the replacement process just to get another yellow screened iphone.
Entraik - what are you comparing it to? Most phones will look great till you compare it to another 3G S or 3G.
Timb - did you get your new phone via overnight yet? Anxious to hear the report on it.
Yes, I think there's a batch of defective screens. This is NOT normal.
completely normal, have compared lots of ipod touch 2g and they all differ in the same way, some a little yellowisher than others...
https://forums.macrumors.com/posts/6948136/
The first thing that I noticed was the yellow screen compared to my 3G. Upon further inspection, the bottom of my display is much more yellow than the top. If the display was uniformly yellow I wouldn't think much of it. But since the display is much more yellow at the bottom I think that it is more likely a defective display.