Which primary colour pair is more suitable for producing a clean bright violet?

Correct answer: Bluish red and reddish blue

The governing concept is colour bias in subtractive pigment mixing. To obtain a clean violet, choose a red that leans toward violet and a blue that also leans toward violet. Their unwanted yellow or green influences are limited, so the mixture remains brighter. Therefore option B is correct. Yellowish red and greenish blue introduce opposing biases and can make a duller, less saturated mixture.