What is the safest action if bubbles form in a wet colour layer?

Correct answer: Remove them with light touches of a clean brush

The governing concept is gentle correction of a wet painted layer. A clean brush, used with light touches, can break or remove surface bubbles while disturbing the underlying wash as little as possible. The brush should not be overloaded with water, and repeated scrubbing should be avoided. Hard rubbing damages the surface, adding paint increases the problem, and folding the paper can create creases or disturb the wet layer.