When can violet appear relatively warm?

Correct answer: When it has a stronger red influence

The governing concept is the dominant influence in a mixed colour. Violet includes red and blue; with more red, it shifts toward red-violet and appears warmer than blue-violet because red is warm. More blue makes it relatively cool. Green changes the hue away from the usual red–blue violet relationship, while white mainly raises lightness or tint and does not by itself create warmth. Hence option A is the only suitable conclusion.