Use three shades for shadowing: taupe for a dark shade, off-white for a medium shade and white for highlighting. Mix each color with water to a watercolor consistency. To make light appear to come from one side, stipple the colors onto the wall in the following pattern: the darker color on the left, the medium in the middle and the light on the right side. Freely dab or stipple the color on the wall, rubbing the color into the surface as you work.
Thin a mixture of creamy taupe and white with water. Using a brush with long bristles, paint the mixture over the pencil lines. The lines should show through to create the look of shadows between the blocks.