I know this is a super late reply, and I don't even know if you still use this website, but I had your exact same issue with the same monitor that you had. After troubleshooting everything, I could not find a single thing wrong with either the monitor or my display settings. However, after maybe a week of research and an endless amount of trial & error, I came up with the idea that it could be because my video card was too outdated or underpowered (which was my last thought, since my GTX 760 is just about 3 years old). After purchasing a GTX 1070 though (and I heard this also works with the 970+ series as well), the issues I had before were almost non-existent. This, and spending an hour configuring my display colors has helped a ton.
I made an account on here just so I could point this out and hopefully help others who may stumble upon this issue.