Why are traffic lights red, yellow, green?

Answer: Red is visible from far away

These are the brightest colors — Wrong. Red, yellow, and green aren't the brightest colors—white or yellow are actually brightest. These specific colors were chosen for other reasons: red was already used for 'stop' in railroads (it's highly visible and associated with danger), green meant 'go' (caution, safety), and yellow/amber was added as a warning transition. The association is now universal and hardwired into driver training.

Red is visible from far away ✓ — Correct! Red light has the longest wavelength of visible light, so it scatters less in atmosphere and fog, remaining visible from greater distances. This is important for 'stop' signals. Red was already used for 'danger/stop' in railroads before cars existed. Green (shortest visible wavelength) meant 'safe/go.' Yellow/amber was added later as a transition warning. This color system is now standardized worldwide.

International law requires it — Wrong. While there are international standards (Vienna Convention on Road Signs and Signals), countries chose red-yellow-green before international law formalized it. The colors emerged from practical needs: red was already used for 'stop' in railroads due to high visibility and danger association, green for 'safe,' and yellow as warning. International agreements standardized this existing practical system.