noun
Refers to a red-colored light, often used in contexts like traffic signals, warning lights, or decorative lanterns. Not as common as 赤信号 for traffic lights.
紅灯が点滅している。
The red light is flashing.
赤信号 specifically means a red traffic signal, while 紅灯 is a more general term for any red light.
Compound of 紅 (crimson, red) and 灯 (light, lamp). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning 'red light'.