Which colour is mixed with blue to make blue-green?

Correct answer: Green

The governing concept is tertiary-colour formation: a tertiary colour is produced by mixing a primary colour with a neighbouring secondary colour. Blue-green therefore contains blue and green, so option A is correct. Yellow mixed with blue gives a greenish mixture rather than the named blue-green in this classification, while red or violet would shift the result toward different hues. The compound name itself provides the key.