How can the colour-wheel position of red-violet be confirmed?

Correct answer: By placing it between its components red and violet

The governing rule is that a tertiary colour occupies the interval between its two named components on the colour wheel. Since red-violet combines red and violet, its position is confirmed by placing it between red and violet. The other intervals correspond to different tertiary colours: blue-green, yellow-orange, or another unrelated combination. The colour name therefore provides both the component clue and the positional test.