When I work this way I usually limit my pallete to 3 primary colors. However, to get the skin tone correct for the Balinese ladies I added Burnt Sienna to my 3 primary colors. So the colors used in this painting are:
Winsor Blue Red Shade
To insure that my palette would work, I painted two of the ladies faces first using each layer in the same method as the rest of the painting, accept I completed all the layers before going on to work the rest of the painting. When I was happy with their faces, I knew my chosen palette would work.
Now comes the fun part. I worked the entire painting with the first color, Winsor Blue Red Shade. I carefully painted using only this color and the white paper to create all the shapes using only the values of the blue. ("Value" means how dark or how light a color is.) Then I let the painting dry for a day.