Which is the most basic colour-mixing exercise?

Correct answer: Making secondary colours from primary colours

The governing concept is learning colour relationships from simple, controlled mixtures. Primary colours are used as the starting set, and combining suitable pairs produces the secondary colours: red with yellow gives orange, yellow with blue gives green, and blue with red gives violet. Therefore option A is the basic exercise. Mixing every colour is uncontrolled, while using only black or a dry brush does not teach systematic colour formation.