Ok i don't know if you managed to solve that but i was stumbling with the same issue, i have a Samsung c32HG70 monitor and a Samsung 55" KS8000 + Nvidia Graphics card with the same problem.

The only way i found out to solve this was turning all the way up the contrast in the Nvidia settings monitor-> desktop colors.

That fixed the games and desktop colors, the only thing i couldn't fix was the subtitles colors that looks dar white greyish.