Color, brightness does vary across LCDs. You can read reviews that measure this but if unacceptable you should return then for others. Most folk end up with a different model.
No. It's not correctable with settings.
I have two led monitors, i don't think either have really been used that much, a maximum of 4months each i think. But when i switched to a different one[ also around 4 months old I THINK] i noticed that there was a huge area in the middle of the screen that appears greyish on white backgrounds, it is very noticeable on lighter images but not at all on dark, it looks like a patch of greyish/almost blue. So i switched to my other monitor and upon inspection i noticed this one has it too! this one has the greyish area on the right hand side. I've attached an image of what they appear like when on a fully white screen.