Which colour is generally warmer between red and green?

Correct answer: Red

In traditional colour theory, red is classified as a warm colour, while green is generally placed in the cool group, although some yellowish greens may feel warmer than blue greens. For this basic comparison, red is clearly warmer than green. Therefore, option B is correct. Option C is incorrect because the colours do not have the same usual temperature classification, and option D is incorrect because neither is normally treated as neutral.