I would honestly recommend people not run these yellowing "tests". If you don't notice the "yellowing" or discoloration normally, then you'd never know. When I first got my SR MBP 2.2 I had heard and read about this issue, so one of the first things I did with my new MBP was to run the test. And sure enough it was a little yellowed, but I had not even noticed it before. I never returned it, but for a while it bugged me and I kept thinking about it. Now is doesnt even bother me and I really don't even notice, except maybe when the entire screen is grey... which is never.
Funny enough, I ran the same test of my desktop's LCD, Samsung xxx. I've had this setup for over 4yrs or so and I never heard about the issue before and honestly never even thought about it or noticed it on the display. Man, when I ran the test... the Samsung was very yellowed, terrible. I would have returned that one if I knew about it. Having never heard of the issue and what to look for I actually never noticed it under normal usage.