Which colour is considered dominant in red-violet?

Correct answer: Red

The governing concept is the dominant component named first in a tertiary colour. Red-violet occupies the transition between red and violet, while the school-level naming convention treats red, the first-named colour, as the stronger influence. Consequently option B is correct. Green, blue, and yellow are not the two colours identified in the compound name and therefore are plausible but incorrect distractors.