A red title is placed on a blue background in a poster. What is the main reason the title stands out?

Correct answer: There is temperature contrast between warm red and cool blue

Warm red placed against cool blue creates a strong temperature contrast, so the title separates visually from its background and gains emphasis. This contrast supports poster hierarchy by making the headline noticeable. The colours are not the same temperature, blue is not automatically brighter, and red is not always the lightest colour; those claims cannot explain the effect.