What is the best correction while wet if an area becomes darker than intended?

Correct answer: Lift excess colour with a clean damp brush

The governing concept is controlled colour lifting during a wet painting stage. A clean, slightly damp brush absorbs some of the excess pigment and gradually lightens the dark area without adding new colour. The brush should be rinsed and excess water removed between lifts. Adding black or thickening paint would make the area darker, while rubbing could damage the surface.