Green light

Origin

The phrase "green light" vividly evokes the command to proceed, a direct metaphorical translation from the traffic signal system that revolutionized urban movement. Invented in the late 19th and early 20th centuries to manage the growing congestion of horse-drawn carriages and, soon after, automobiles, the traffic light system used colored lamps to communicate clear instructions. Green quickly became the universal sign for "go," a clear visual cue for drivers and pedestrians alike. This straightforward, widely understood directive swiftly moved beyond the intersection, permeating language as a concise, powerful idiom for granting permission or initiating action, making it an essential part of modern communication.