EDIT PullusPardus: I’ve messed about the settings a bit ,and found the best tweak so far especially for Source engine games like the one you are playing , when you have the “Sony Levels” put on the following
Input start : 0.007
Input End: 1.000
Output Start: 0.041
Output end: 0.925
Gamma: 1.007
After that don’t forget to rename this setting and save it to whatever name you’d like, this setting not only makes the colors better but also make the black areas better.
I found the original answer here: http://forums.creativecow.net/thread/24/938734