After playing Xcom Windows seems to be stuck in basic colour mode. It isn't the theme, because I've switched to aero, basic, and my default, but for some reason it's now set to a lower colour mode and I can't for the life of me find out how to change it back. I've googled the hell out of it and everything just regurgitates the Aero theme thing.
If I'm not making it clear what I mean, where I should have nice smooth colour gradients I now have varying patterns, like a GIF saved for web with too few colours. I can post a screenshot if need be, but hopefully someone will know what I'm on about and be able to help.
Colour depth settings are in Personalization -> Display Settings for me.
You could also have a look in 'Adjust Visual Effects' under 'Performance Information and Tools' (or similar, I'm on Fista here), or making it run the Experience score tests again.