It works fine for me, in VS2012:
What you're looking for is the User Types (Value types)
color in
Tools -> Options -> Environment -> Fonts and Colors
If that doesn't help, you should check that you don't have an external addin that might be changing the colors...
Update - based on your comment - if you're using the Productivity Power Tools you might need to disable the Colorized Parameter Help Option from Tools -> Options -> Productivity Power Tools -> Colorized Parameter Help
...
Another option is to try to Repair your installation of VS2012