This is a lesson I did with my oil class which makes the most of the ground, (an undercoat of either oil or acrylic paint that acts as a base colour for your painting). Grounds can be used with any other type of paint too. It can be quite sterile and harsh to paint onto a white canvas, a ground can soften the blow and allows your painting to look finished more quickly. The colour you choose can play a huge part in the overall effect and mood of the painting. You can also leave your ground showing to a greater or lesser degree. Here the ground colour has been left untouched to become the shadows of the flower.
In this exercise, I suggested a really strong blue, one that is often found in shadow colours,