Drawing cafe

On the weekend, my friend and I went to a drawing cafe in Bangkok -- customers can paint with colored cream on the cake. First of all, we need to choose from three different cake bases: Christmas color case, lemon flavor taste base and full chocolate cake base. My friend and I both chose lemon flavor one, and the got a plate of different colors of cream, but only red, yellow, blue and white were used as the basic color, which means we need to mix the basic colors to create different colors for example for green, we need to mix yellow and blue and a bit white.