Which tertiary colour is formed by mixing equal amounts of red and orange?

Correct answer: Red-orange

The governing rule is that a tertiary colour is named from the primary and adjacent secondary colours used to make it. Red is a primary colour and orange is the neighbouring secondary colour; equal mixing therefore gives red-orange, which lies between them on the colour wheel. Option A is correct. Yellow-orange requires yellow and orange, red-violet requires red and violet, and blue-violet requires blue and violet.