If green made from yellow and blue appears too cool what should be increased to make it warmer?

Correct answer: Yellow

The governing concept is adjusting colour temperature by changing the dominant component. Green made from yellow and blue appears cooler when the blue influence is too strong. Increasing the yellow proportion shifts the mixture toward yellow-green, which is generally perceived as warmer. Black would mainly darken, white would mainly lighten, and violet would introduce a different hue and may complicate the mixture. Therefore increasing yellow is the most direct and controlled correction, making option B correct.