This is a quick study of the 6-hour pose. Based on an article I read in the May issue of The Artist Magazine by Felicia Forte, I followed her technique of painting a portrait using just 4 colors: titanium white, ivory black, yellow ochre and cadmium red.
The procedure is drawing the shapes, establishing light/shadow patterns, put in the local skin color and the local shadow colors and finally refining. All four colors are used but in varying degrees depending if it is shadow or light. For instance, the shadow consist mainly of black and red with a touch of yellow. The skin in the light is made up of red and yellow with a touch of white. Highlights are mainly yellow and white with a very touch of red.
This article helped quite a bit as how to use the colors more effectively.
And this is 6 x 8 on canvas paper.