What is produced by mixing blue with its adjacent secondary colour violet?

Correct answer: Blue-violet

The governing concept is the naming and formation of tertiary colours. Blue is a primary colour, and violet is the adjacent secondary colour on the colour wheel. Mixing these neighbouring colours produces blue-violet, so option C is correct. Red-violet would require red and violet, while blue-green requires blue and green. Yellow-violet is not a standard neighbouring primary-secondary pairing in this context and is not the expected tertiary result.