If two different blues produce different greens with the same yellow what is the main reason?

Correct answer: The two blues have different colour biases

The governing concept is colour bias, meaning that a pigment may lean slightly toward another hue. A green-biased blue mixed with yellow usually produces a cleaner, brighter green, whereas a reddish or violet-biased blue introduces red, which dulls the mixture. Thus option A is correct. The yellow is held constant, green is made from blue and yellow, and the colour wheel is not the cause of the variation.