I was thinking that same thing but since the OP had the same issue with another device and it is something you would manually enable I didn't suggest it.Are you by any chance using blue light filter?
Try in safe mode just to be sure no issues from 3rd party appsNo its not on
I'm out of suggestions. Could be a bad display. Originally I was going to suggest posting a screenshot to determine if was software or hardware because a screenshot doesn't show hardware defects, but that won't work because I tried it on normal and warm and the screen shot always come out normal.No issues wirh apps