Update: Restore via iTunes to download a new version of the firmware (2.0, 5A347). The colors will look much better after you restore. The shipping firmware on the iPhone 3G is 2.0 5A345. After the restore, the colors will be close to v1 iphone colors. posted by tamakin
Update #2: Some have posted that update #1 doesn't solve the issue, the theory is back to bad consistency between various screen manufacturers.
After waiting in lines and going through the excitement many are reporting that their 3g iPhones have noticeably yellow screens.
In the picture above the iPhone on the left is 3g, while the one on the right is a 1st generation model. If you remember back a year ago to the original iPhone launch there were two different screen types. One was perfect and crystal clear while the other had small but noticeable white dots. Once again Apple's quality control processes seem to be lacking leading to these disgusting yellow screens on many units.