Strange brightness/color/tint issue on iMac Retina

[MowingDevil]

Any adjustments around startup/wake are perfectly normal. If these changes happened later while you are working then I'd be concerned.

 

[jayco1983]

Right, so I had the iMac exchanged after discussing it for a while with Apple. Got a new one and the same "issue" remains, so I'm guessing it's quite normal. Or something.