Matching real rock color and patterns onto plaster and foam

Here I have matched the real stone patterns and colors (on the left) to plaster rock castings (the two smaller pieces to the right) The plaster was white to begin with. I used acrylic paint washes. There are several stages to this replication so I documented the color palette / ratios and instructions as seen in the photograph of my notebook. The procedures for painting foam were a bit different than that of plaster, but very similar.