Why do planes have coloured lights?
Planes have a red light on the left wing, a green light on the right wing and a white light on the tail. Each one can only be seen from its own side.
A red light on the left wingtip, a green one on the right and a white one on the tail tell you which way a plane is going at night.
Red, green, white
The left (port) wingtip has a red light, the right (starboard) wingtip has a green one and the tail has a white one. Each shines only in its own direction, like the lights on a boat.
Reading the lights
Red and green together mean the aircraft is coming roughly towards you. Only white means it is going away. Only green or only red means you are seeing one side of it as it crosses in front of you.
Flashing lights
Bright white strobes on the wingtips and a flashing red beacon on top make the aircraft easier to see. The beacon is usually switched on just before the engines are started.