Which warm colour is commonly seen in flames?

Correct answer: Orange

Orange is a warm colour and is commonly used to represent the visible glow of flames, especially together with red and yellow. It suggests heat, fire, brightness, and energy, so it fits the visual idea in the question. Blue, green, and violet are generally classified as cool colours. Some real flames can show blue areas, but in basic art education orange is the conventional flame colour. Option C is correct.