Update: after going to all this trouble, I found a link online at http://www.genesisoilpaints.com.au/pigment.htm . Oh well.
Genesis color index names are nowhere on the web that I have found, though most of the paints come with them labelled. Here are the colors I have with the CI numbers. I tried to get only the pure pigments, not the tints. By and large, I’d say they use pretty good pigments. I also got the thick medium and will try mixing pigments directly into that. Update: I had no problem mixing chromium oxide green with the thick medium, so this seems like a workable solution to customizing colors. It should be safe to use any pigment used in encaustics, since they are heated as well.