Which of two blues will be considered relatively warmer?

Correct answer: A violet-biased blue

The governing concept is temperature bias within a colour. A green-biased blue moves toward yellow, a warm influence in this comparison, while a violet-biased blue contains relatively more red but is conventionally the cooler blue choice when the comparison is based on blue’s warm–cool bias? Actually, among two blues, a violet-biased blue is generally warmer because it leans toward red. Thus B is correct; black changes value, not necessarily hue temperature, and the blues are not always equal.