I use pigment paints. I am basically making period gouache, which is a type of heavily pigmented watercolor. I use powdered gum arabic, water, and the dry pigment. You mix it so that a sample on a note card is neither shiny (too much gum arabic) nor too dry (it will come off on your finger when you brush it). And for consistancy, I make it so it is about like a good gravy.
What I don't know is how the stuff will marble. It IS heavily pigment dense...Iris might be able to help you there.
If you need a reference book, you can use Cennino Cennini's book for it...
Email me if you want more than that, some of the pigments aren't water soluble, I can help you with that.