Wow, havn't seen this mentioned forever.
Used to happen to me when using older computers a lot. Trying to remember a solution.
Check your display settings when it happens to ensure the colour is set up properly. If that doesn't work try resetting your screen resolution. Last thing to try is run another program full-screen and exit, it may also reset things for you.
Might I add that I am using a brand new computer:
HP Pavilion dv6z-3000 CTO Select Edition
AMD Phenom II X4 N930 ~2.0 GHz
6 GB RAM
ATI Mobility Radeon 5650 1GB VRAM
Windows 7 Home Premium 64-bit