What should I use to color epoxy?

I saw an artsy project on the TV show Surprise By Design that I want to try. They took epoxy, mixed it up, added some liquid coloring agent and poured the result into ice cube trays. An hour later, out popped little rectangular “gemstones.” (They then used these to decorate a truly hideous mirror.) But it’s not a project on their website, and I didn’t catch exactly what the coloring agent was.

So what would you suggest I mix into the epoxy to color it? It should remain transluscent, and be available in gemtones, obviously. And cheap is good.

I don’t know, but if you find out, tell me. I have some epoxy-related projects in mind, and coloration could help.

Probably food-coloring…

Well, there’s this: http://www.evsupply.com/ffaq.html

and this: http://www.engineeringlab.com/epoxykit.html (scroll to the bottom)

and this: http://www.jamestowndistributors.com/ak/Epoxy/Polyester_Resins/Coloring_Agents_fam/

I’ve seen recommendations for oil paints (or oil-based dry pigments); don’t use pre-mixed paints if you’re actually planning to use the epoxy as an adhesive.

Brilliant! Thank you!