What is the advanced benefit of keeping two different reds in a limited primary palette?

Correct answer: A warm red helps clean oranges and a cool red helps clean violets

The governing concept is a split-primary palette based on pigment bias. A warm, orange-biased red mixes more cleanly with yellow to produce orange, while a cool, violet-biased red mixes more cleanly with blue to produce violet. The two reds do not make pure green, cannot replace blue, and are not restricted to shadows. Their purpose is cleaner, more vivid secondary mixtures.