What is the best way to preserve colour brightness during blending?

Correct answer: Use clean colours, limited mixing and a clean brush

The governing concept is colour purity. Brightness is preserved when clean pigments are mixed only as much as necessary and the brush does not carry muddy residue from another colour. A clean palette also prevents accidental dulling. Adding black usually reduces brightness, repeated rubbing can disturb the surface, and mixing every colour together produces a muddy result. Thus, option A gives the best practical method for maintaining clear, lively colour during blending.