Heiko,

I've been dabbling with red, yellow and blue pigments to create a translucent epoxy/fiberglass coaming layup to match some Honduran mahogany. It's going well, though color richness is proving challenging.

You have options to create a layup that is opaque, translucent or transparent. If you're trying to color a wooden hull a dark, rich color such as aubergine it will definitely be best to stain the wood prior to laminating with epoxy and fiberglass. This is true even if you color the epoxy. It's also true whether you are trying to achieve an opaque or a translucent finish. I would bet a rich translucent eggplant-colored cedar kayak would catch a lot of looks.

You can attempt to do the job by coloring only the epoxy but it's difficult to achieve a uniform result when it's so thin. The subtle variations in epoxy thickness with a thin lamination tend to make things look somewhat blotchy. If you're trying to achieve an opaque finish, you may have to build up the surface with a lot of pigmented epoxy. Remember that epoxy must be pigmented only in limited amounts or it will be weakened.

I got some transparent pigments from TAP Plastics because there's a store close by. The transparent and opaque epoxy pigments are easy to get from a variety of sources though.