In my experience, viewing an AMOLED from an extreme angle can show hue's, usually pink. On the other hand, if you are looking at the phone head-on, and on an even color background you see portions of the screen significantly more pink or yellow than the others (those are the most common issues), then you probably have a defective screen. Google "Galaxy S6 screen tint" and you will see this is not uncommon. I have also heard the screen adhesive can cause these tints, and takes a few weeks to burn off, but I'm not sure how one would confirm that.
I also have read that the screens that get cut closer to the edge of the presumably giant OLED wafer to make all the phone screens have worse performance. Again, just something I have read, not sure how much truth there is to that.
I do know that as soon as I get my 6P, the first thing I am going to do is check my screen on white an light grey backgrounds, and if there is any significant uneven tint, it's going back because I am extremely sensitive to that sort of thing, and it's not something you can "unsee". Use google images to search for an 18% grey solid image, and it should be pretty noticeable. The WhatsApp standard chat background and anything pure white is also good for testing.