Which colour pair produces red-violet?

Correct answer: Red and violet

Red-violet is a tertiary colour produced by mixing red, a primary colour, with violet, the adjacent secondary colour on the traditional colour wheel. Hence option C is correct. Red and orange produce red-orange, blue and violet produce blue-violet, and yellow and green produce yellow-green. The adjacent primary-secondary relationship is the governing concept, so a pair is correct only when its two colours occupy neighbouring positions and correspond to the named intermediate hue.