What may happen if a dirty brush is placed in a watercolour pan?

Correct answer: The colour may become contaminated

The governing concept is preventing colour contamination. A dirty brush may carry leftover pigment, muddy water, or another colour into the watercolour pan. That material mixes with the stored paint, so the colour may become impure or dull; therefore, option C is correct. A dirty brush does not make paint brighter or dry faster, and it cannot change the physical size of the pan. Rinsing before picking up paint protects colour clarity.