Does the color of a light change how fast you react to it? You build a circuit with three colored lamps and a digital timer. When a lamp turns on, the timer starts. The participant hits a stop switch as fast as possible. You test 20 participants seated 5 meters from the lamps. Green produces the fastest average response at 0.69 seconds. Red produces the slowest at 0.78 seconds. Amber falls in between at 0.73 seconds.