Painting with the paintbox
Primary and secondary colours:
The relevant secondary colours can be mixed using two adjacent primary colours.
Multiple thin layers of colour are placed one over the other in several steps.
Apply wax on the paper before painting and the wax repels the topcoat. That's practical physics in the art class.
In everyday use in schools, we often notice that some colours are used up faster than others. That's why the paints can be purchased individually so there's no need to re-order an entire paintbox.