just to throw in my 2 cents
I went to the Apple store today for this same exact issue. My Verizon iPhone 4 has a slightly yellow/creamish tint. It's not nearly as bad as the attached picture posted above but it is definitely noticeable even without a normal phone to compare against. I took it into my local Apple Store and surprisingly, they immediately agreed that the screen was tinted. However, they only offered to replace the phone with a refurbed (non retail) phone. They assured me that it was brand new since they (supposedly) haven't gotten any actual refurbished Verizon iPhones since it is too new. I am still within my 30 day return policy so I insisted on a brand new sealed retail box. They said that it could not be done via the Genius bar so the only option I have is to return the phone and repurchase if I want a sealed retail box. And since I bought it on Apple Online Store, they said I'd have to do the return via the website.