An artist wants yellow-green to look more like natural grass. What should be done?

Correct answer: Increase green

The governing concept is controlled colour mixing within a tertiary hue. Yellow-green contains yellow and green; increasing the green component shifts the mixture toward the foliage-like appearance commonly associated with grass. Thus option B is the best answer. Adding more yellow would make it brighter and more yellow, while red or violet would neutralise or alter the hue instead of making it greener.