Draw 6 spheres on one page using colored pencils using the different color combinations to show a variety of values.
Creating: Then on the circles, lightly hatch and crosshatch, gently building up layers of "dry glazing" to create a sfumato effect of chiaroscuro, the six different sets of analogous colors. Figure out which color is the lightest, mid-range, and shadow. Remember the 5 steps of chiaroscuro: highlight, halftone, shadow, reflected light, cast shadow.
For example, with the combination of yellow, orange, and red, yellow will be the highlights, orange will be the mid tones and reflected light, and red will be the shadows.
Color Theory: Refer to the color wheel chart below.