Hi Gary
I use ground pigments for my frescoes. I obtain them either from from Bayer (cement tinters) or from Maimeri (an Italian company- I by them through Sebino- an art prducts manufacture- see on the Internet). It saves me a lot of time which I need terribly for the jornatas process and generally I try to save time and effort for the painting task by bying ready materials that I can rely on and after checking them like ,for instance lime.
Good luck Yoram