UPDATE:
After having no luck with the Geniuses, if finally called AppleCare last Friday afternoon. I explained to them the the issue with the yellow screen and that the Geniuses were no help. The guy on the phone was very cool and he seemed to be concerned about me being unhappy.
He offered to swap my 4s out at no cost.
Monday morning I had a replacement iPhone 4s delivered at my workplace. WOW!!
The replacement iPhone does not have the yellow screen issue. The screen looks great. The colors match very closely to my my iMac display. It's slightly warm, not blue, and definitely not yellow!
One little thing I noticed on the replacement 4s: The little gray square on the Home Button seems to be a little crooked or slightly rotated. It is noticeable by people who pay close attention to detail (like me) but it's no big deal. I'm not going to complain about that.
FYI: The serial number of the yellow screen 4s starts with C35. The replacement one starts with C38.