You mean you want to make a plugin with it?
Well, you just go into the plugger and fill in all the stuff, and then when it gets to a place that has a drop-down menu of transparency settings, choose either lightest, or darkest (one is for white, the other for dark... I just can't remember which one is which!
There are also some FAQ's about it: http://fxhome.com/forums/viewtopic.php?t=5410http://fxhome.com/forums/viewtopic.php?t=3082http://fxhome.com/forums/viewtopic.php?t=6907
P.S. If you need help, feel free to email me the plugin and I'll fix it up for you.
[EDIT] Oh... wait you said Flash? or what? Now im confused... would you mind explaining more?