now, what i want to do (in the not to distant future) is to create my own custom figures. Mike Buckley re-inspired me to try and go through with this. I dont want to do 12“ figures though, i want to do 3 3/4” figures now. easily, what i plan on doing is taking old cheap figures and changing the bodies and heads and possibly taking other accessories from other action figures and editing them to my liking.

my question is, let's say i get a GI JOE COBRA TROOPER action figure and i want to change his suit to beige. If his suit is already blue, will the paint go right over the blue, or will it mix and create and akward color? or is there some kind of paint that i can buy that will go right over the exsisting color without mixing?

Try using gesso. Coat your figure with it (be sure to use masking tape over the parts you DON'T want to get covered!) and the paint should stick to the surface. Makes your life much easier.