What do colored lights on a boat mean?

Theyre used for boating at night. They tell other boaters exactly where the frontend and backend of ur boat is and how long the boat is. so they dont hit u at night. If i remember right the green light goes on the front end of the boat and the red light goes on the back.

The red lamps are displayed on the left (port) side, and green on the right (starboard). A large modern ship, like maybe a tanker or container ship, will probably have several coloured lamps down each side, so that a smaller ship can't mistake where the ends are.
An old saying as a reminder for the colours is, "there is a little RED PORT, LEFT in the bottle".