This way of painting is a great way to get a better understanding of shadow shapes and changes in value. To begin you will want to find an image for reference, one with strong changes in value. Begin to lightly sketch out the different shapes of value that you see.
Once your drawing is done you can begin to mix your colors. Use any color palette you would like. Now you can begin to fill in the shapes with different colors, as I show you in the demonstration.
Other supplies used:
HB Mechanical Pencil
The struggle to be original hates conformity, but the struggle to be better disregards it, or takes advantage of it to build workable conventions. -Darby Bannard