meh i dunno… i think i mightve seen a bit of code defining the alpha color of a sprite in gamemaker… i might be wrong though. im really not a good coder, anyway 
You can use draw_set_blend_mode_ext(modeA,modeB) to specify what what colours to use as what. I’m not sure exactly how … but I was able to switch the transparancy colour on it using something like draw_set_blend_mode_ext(color,bm_src_alpha) or something like that … I came across the effect when I was trying to make the flash-effects in my game. Theres a lot of blending modes to try, if you play around with it you might be able to figure it out.
We only need one Game Maker help topic, and, after flipping a coin, the other one will be the one that stays. 
Continue discussion over there, and to quote someone from here, just copy/paste his or her text and stick it in quote tags over there. Put in his or her name if it helps.
I’ll keep this in the fangames board for another week or so (unless I forget to move it to the wasteland) so you can continue discussion as if nothing happened a little easier.