For the tempera lesson, I provided only primary colors, brown, white, and (lastly) black (for shades in the toppings). The background is done in marker. Each scoop of ice cream has to be a different tint (flavor).
My sample painting:
For the oil pastel lesson, blending is key. Again the scoops all have to be a different tint (flavor). Even if the students used pink I asked them to add white to tint it even lighter. Required number of scoops: three or more.
A few student examples: