I use acrylic paints. I can get a set of small tubes of different colours-10 tubes from a shop called The Works here in England for £2. I don't know if you have a similar craft shop in the USA
Mike
I use the acrylic craft paint that are about $1 at Michaels or any craft store. You don't need every color, they mix well. Sometimes I even use a small drop in my epoxy to tint it.