So what would be used to mix in with resin to change its pigment? I have sculpted a crystal, needs to be sanded and smoothed.... I made it with 10 sides...oops

From what I can tell the show ones are all 6 sided. Gonna make a mold with some soft goopy stuff I have and try my hand at making a few with clear casting resin, but I'd like to make some colored ones as well, didn't see anything to tint at michaels. Any help is always appreciated.
Working on customizing my car with a stargate theme.
Progress reports as they come.