Which pair is suitable for making a clean violet in a split-primary palette?

Correct answer: Cool red and reddish blue

A clean violet requires a red and a blue that both lean toward violet rather than toward yellow or green. Cool red is generally less yellow-biased, and reddish blue already moves toward violet, so option B is the appropriate pair. Warm red and warm yellow favour orange, the cool yellow–greenish blue pair favours green, and option D introduces a warm yellow influence that can dull violet.