What should be added if violet has become too red and needs balancing?

Correct answer: A little blue

Violet is a mixture of red and blue. If it appears too red, the mixture has a relative shortage of blue, so adding a small amount of blue restores the balance; option A is correct. Yellow or green can neutralise and dull violet because they introduce a contrasting yellow influence. White only makes the violet lighter and does not correct the red-blue ratio. Small additions are important because too much blue can make the colour overly cool.