Latex or acrylic paint, using either a brush or roller.

House paint is mostly latex, and artist's paints come in acrylic.

Tempra or watercolor would just wash right off.

Spray paint eats foam, so only use it if you're trying to get an effect, and be aware that you may end up dissolving your foam!

__________________
I'm a Halloween Bride! 10/31/2002

Where there is no imagination there is no horror.
~Sir Arthur Conan Doyle