So I was on my 2nd Nexus 6P and like the first it had an uneven screen. Normal/slightly pink at the top and at the bottom it's more yellow. Instead of returning it I've decided to try and fix the yellow tint by intentionally causing a burn-in on the over-enthusiastic green pixels in the bottom half of my screen.To do this I flashed a kernel which unlocks the high-brightness mode of the display, the awesome EX kernel, set my screen timeout to 15 minutes and left the display turned on for 3x15 minutes in high brightness mode with a black-to-green gradient open full screen in the Photos app (absolutely nothing else on screen). After each of the 15 minutes I checked the progress, after the 3rd time I considered it done. I'm happy to report that this has nearly eliminated my uneven screen problem.So far I've seen no ill effects, just a nice even screen.I used this black-to-green gradient that was a close match to where my screen was yellow. My first 6P had a different pattern of yellowness, so that would have required a different gradient, more like black-green-black.