Found this ultimate geek utility which only changes the color of the Windows Vista or 7 Aero borders based on local temperature (or conditions).
Tried it out and it does what the authors say - simple one-click installation, then enter the US ZIP code of the temperature you want to control your display, and that's it!
http://spikex.net/2010/04/aeroweather-weather-based-aero-color/No essential purpose but fun - but then, who doesn't enjoy out-geeking their neighbors from time to time?