What may happen to green if red enters a yellow and blue mixture?

Correct answer: Green may become muddy or dull

Yellow and blue combine to make green, a secondary colour. If red enters that mixture, all three basic colour components are present, so the green loses purity and brightness and may become dull or muddy. The added red does not purify the green, turn it white, or change its classification into a primary colour. Thus option B is correct. The governing concept is that an unintended third colour, especially one opposing the existing hue, reduces the clarity and intensity of a paint mixture.