Which colour is complementary to primary blue?

Correct answer: Orange

On the traditional RYB colour wheel, complementary colours lie directly opposite each other. Blue is opposite orange, so orange is the complementary colour of primary blue. Green and violet are neighbouring colours related to blue, while yellow is another primary colour but is not opposite blue in this model. Therefore, option A is correct. The standard pairs are red–green, yellow–violet, and blue–orange.