Why does blue appear clearer against a red-orange background?

Correct answer: Because of warm-cool contrast

The governing concept is warm-cool contrast, which increases visual separation. Red-orange belongs to the warm group, while blue belongs to the cool group; placing them together makes their different temperature impressions more noticeable, so blue stands out clearly. Option B is false because their effects differ, option C misclassifies blue, and option D describes blending, which would reduce clarity rather than improve it.