Alt Bike Culture - Helmet Painting

So, I was thinking of personalizing my helmet, but then realized this might be harder then I thought. I am worried that acrylic paint would not stay on the plastic, and that spray paint might eat the Styrofoam. Any ideas/suggestions?

I'm being lazy but I know from reading Sheldon Brown's web page, he painted his Bell
helmet red. (he even added a little plastic eagle, kaiser-style). just google him

So, I was thinking of personalizing my helmet, but then realized this might be harder then I thought. I am worried that acrylic paint would not stay on the plastic, and that spray paint might eat the Styrofoam. Any ideas/suggestions?
If you're concerned about the styrofoam part, you can separate the plastic from the styrofoam, albeit with a bit of a struggle sometimes. The plastic can be painted with regular enamels, once the surface has been scuffed up (240 or 320 sandpaper). Just be careful not to flex the plastic shell when you put it back on the helmet, as the paint will probably come off in a sheet.

I've been considering it too, you could always, sand it down and use some colored primer and then have at it. Personally, I opted for custom decals made.