Interesting. I just did the same thing but my screen looks exactly the same.
Might it be a placebo effect on your part perhaps? Would you mind taking a photo?
Here's there the old mac (country desktop background, 4778) and the new iMac (fish background, 4790). Let me know what you think. It's not "perfect" but much closer. Less yellow tint on the right side. The pictures don't do enough, it's much more apparent in person.