Which colour relationship forms red-orange?

Correct answer: A mixture of primary red and its adjacent secondary colour, orange

The governing concept is tertiary-colour formation on the traditional colour wheel. Red-orange lies between red and orange, so it is made by mixing the primary colour red with the adjacent secondary colour orange. Option B is correct. Red and green are complementary, red mixed with blue moves toward violet, and orange with green would produce a different intermediate hue rather than red-orange.