I went to our neighborhood Hobby Lobby the other day and picked up some Testor's spray paint in the car model section. It says on the can it is safe for styrofoam. I tried it on some blue fan fold both with the plastic film on and an area with the plastic film stripped off. No damage to either area! It is a little expensive at $2.68 for a 3 ounce spray can, but I will tell you the coverage is surprisingly good. One coat should do it. I bought a chrome color for another Blu Cor fan-fold Mustang I'm going to build. Try it, it works!
RCNutt