Recently I have noticed that some games make my screen go darker. It happens with a selected few, but it is there. What I mean by going "darker" is that once I quit the game (not while playing) I notice that my desktop background pic gets darker, and from that point on everything else I play is actually darker. The first time I had this happen to me was when I was playing seven core (
Sevencore - Overview - Massively Multiplayer Online Role - Playing Game List - MMOsite.com)
It happened after I left the game at the log-in screen. I have never heard of a similar issue before, so I don't know how to troubleshoot it. One more thing, when I restart my PC things go back to normal.