Red, green, stop, go, why?

Red means stop. Green means go. Why? Why? Why?

-- L., Leucadia

You'd prefer maybe a nice Navajo white and, say, maybe a deep mauve? Spare us designer traffic lights, please. If you want the very old weird logic behind it, consider the ancient associations of the color red with war, specifically, and danger in general-- spurting blood being a universally recognized sign that something's not going as planned.) Newer weird logic is railroad logic. Red lights became the standard stop signal for trains by the middle of the 19th Century. Red's complementary color, green, became the go sign. When Cleveland installed the first electric automobile traffic signals in 1914, they just borrowed the already established railroad colors.