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

Correct answer: Cool red and reddish blue

The governing concept is split-primary colour mixing: pigments with a colour bias toward the target hue produce a cleaner mixture. Cool red, such as a red leaning toward magenta, and reddish blue, leaning toward violet, contain little yellow influence. Mixing option B therefore supports violet, whereas warm yellow or greenish blue introduces yellow or green bias and can make the result dull or muddy.