Yes there is a built in option in Windows to enable screenshots from a directdraw game without horribly messed colors.
It is a simple registry option that needs to be enabled.
The patches are available here:
http://knights.x10hosting.com/KaM/Downloads/prntscr.zip
(they talk about another game in the readme, but this fix is universal and works for SPMBT too.)
So now you can take a screenshot from the game even if it is running in full screen with the print screen button. Enjoy.