They mean organic pigments like anthraquinones (although aside from alizarin lake, I don't know what else would be in oil paints) and some of the more recent (cheaper) oil paints use large organic molecules, most likely as metal complexes such as in phthalocyanine blue. What pigments are in a paint depends on what colors, what companies, and what age. I have some (30 or so year old) red oil paint from my great uncle that I know is real vermillion red (HgS...I intend to eventually experiment with one of the tubes), but no company that I can find will sell it anymore for obvious reasons. Most modern "mineral" reds are Cadmium Selenide blended with Cadmium Sulfide. Most also have an inert batrium salt thrown in. Old greens may be Paris green- a blend of copper acetate and arsenic trioxide. Again, you wont see it anywhere today.