Step 1: Work in pencil to lightly figure out proportion and cross contour lines.
Then use a white color pencil to define the face using cross contour lines.
CAUTION: This surface will allow you to do a small amount of gentle erasing, but if you get too aggressive you will go through to the other side and have white to deal with.

Step 2: Add a light value to the side facing the light source.



Step 3: Select your color scheme and deliver a medium saturation to your cross contour sections - be sure to work in the same direction as your cross contour lines.



Step 4: Deliver additional colors from your color scheme, try to establish a pattern for visual unity and rhythm.



Step 5: Work on contrast - go back through your mask to develop contrast.
I added white to my light side (overlay or layer with the base color as needed) and a darker value analogous color to my dark side (purple, dark green, and blue violet).
The colors will need to be highly saturated to show up well on black.