If a green sample appears darker after drying, how should the next mixture be adjusted?

Correct answer: By making a slightly lighter mixture

The governing concept is practical colour mixing and adjustment after observing a dried test sample. If the dried green is darker than intended, the next wet mixture should be made slightly lighter, because drying may deepen or alter the apparent value. Adding black would make the problem worse, while mixing all primaries or blindly repeating the recipe does not provide a controlled correction. Thus, option B is correct.