Which colour will not be formed if red and yellow are not mixed?

Correct answer: Orange

The governing concept is the traditional colour-mixing relationship for secondary colours. Red mixed with yellow produces orange, so if those two colours are never combined, this particular mixture cannot be formed. Option B is therefore correct. Green is associated with yellow and blue, while violet is associated with red and blue. Blue itself is one of the traditional primary colours, so it does not require red and yellow to be produced in this school-level model.