When running Snow Leopard, you may run into a small problem with your monitor colors where after running a full screen graphic application or system feature such as the screen saver, the colors on the screen will appear washed out and tinted blue. This will not always happen, but seems to be particularly prominent after running applications such as games, or when using multiple displays.
The system will usually apply a colorsync profile to each device that handles color, be it printers, cameras, scanners, or monitors, which allows colors to be corrected and properly translated between devices for consistent output. You can calibrate your own profiles to use, and while the system will apply the monitor's profile, sometimes applications will change this and the system will not properly load the desired profile when they are closed.
This has happened in the past with the release of 10.5 Leopard, and was fixed with updates. It is odd that it has cropped up again, but hopefully will be addressed in the upcoming 10.6.2 update. Meanwhile, you can go to the "Displays" system preferences, and clicking the "Color" tab should reload the selected profile.
One thing that may help is if you consolidate your calibrated colorsync profiles in the global library, rather than keeping them in your user library. To do this, go to your /username/Library/ColorSync/Profiles/ folder and move the profiles listed there to the /Macintosh HD/Library/ColorSync/Profiles/ folder.