This is what it looked like before class.
Using the same 6 colors, I started adding the shadows to add the form. The 6 colors:
Scarlet Lake (warm red)
Crimson Lake (cool red) (note - I often use Pomegranate as my cool red)
Spanish orange (warm yellow)
Yellow Chartreuse (cool yellow)
Peacock Blue (green blue)
Copenhagen Blue (purple blue) (note - I sometimes use Denim Blue or Indanthrone Blue as substitutes).
Note - a 3 color palette I use sometimes is Crimson Red, Canary Yellow, and True Blue.
I continued using the stump to blend the layers (clean between uses)
I use my stik tak and erasers to lift the light areas.
Remember that Peacock Blue and Scarlet Lake make a good dark (and you can add Copenhagen Blue or other colors as needed) . Vary the ratios to vary the color - if you need it to be a dark blue lean it toward blue. If you need it to be a dark red lean it toward the red.