Create your own yellow tint where there is none.

[Sir Cecil]

Go to the link, scroll down to the BLUE square (#5), and keep watching CLOSELY for 30 seconds or so...

http://www.realcolorwheel.com/afterimage.htm

Then move the gray top-bar of a webpage to the top left corner of your iMac screen. The gray bar should be a nice cool gray. Look at it for thirty seconds or so. Then move the gray bar to the bottom right. See the warm tone of the gray in that position? Almost yellow?.

Now LEAVE the gray bar in that bottom right position. Then sit back and LOOK AWAY from the screen for one minute (looking away from any bright light). Then... look at the gray bar again, still at bottom right. Gosh! It's a cool gray!

Of course, this is in no way intended to suggest that the yellow tint phenomenon is all a hoax.

 

[GoCubsGo]

K but why?

 

[Sir Cecil]

K but why?

Because SOME devious types know how to mislead people. And they take advantage of it... with trick tests and optical illusion games.

For every iMac with a genuinely discolored, truly defective screen, I wouldn't be at all surprised if 100 have been returned for no other reason than that people are seeing things. Too many blueish pixels for their poor little eyes to cope with... leaving imaginary yellow streaks all over the place.
Disagree?
Then do the blue test at the top again. It's every bit as clear as anything in that infamous "Test for Yellow Tint Issue" thread that has panicked the world.
Or ask why, when you first look at your computer each morning, it's sparkling clean, but goes "yellow" after a few minutes staring at the screen. It's not the screen "warming up" that causes it. To prove that, simply turn on the screen a few minutes before you look at it for the first time in the morning. At first look, even if the screen has been on for an hour or more, it will look clean and white – for a while, until your eyes do what comes naturally.