is this possible with scripting or i dont know...magic?
Yes, there is a way.
You adjust the contrast of your monitor... :P
TintScreen(100,50,0);
Will let the screen look like an aged photo.
Scotch did a great plugin for this, it comes with controls for Grayscaleon() and grayscaleoff(). it only runs in 32bit games though. other than that, no probs.
http://www.agagames.com/scotch/ags_bandw.dll