Vallejo Acrylic Model Color Paints.
These are water-based paints which are non-toxic and non-flammable and come in a 17ml eyedropper bottle which prevents spills.
Model Color is specially formulated to adhere to Plastics and Polyesters. All shades dry to a matte and opaque finish barring metallic and transparent colours.
Model Colors can be diluted with water, and are easily mixable. Errors can be corrected immediately with water, or with a small amount of alcohol. Once paint has dried, it is waterproof and permanent.