Navigation rules require that powered boats under 65.5 feet long (20 meters) exhibit specific minimum lighting while underway between sunset and sunrise. According to the United States Coast Guard, this lighting includes red and green sidelights, which can be separate or combination lights, as well as a masthead light and a stern light.
The masthead light must be white, located at least 1 meter above the sidelights and facing forward. It must be visible up to 1 nautical mile for powered boats under 39.4 feet (12 meters) long, and 2 nautical miles for powered boats between 39.4 feet and 65.5 feet. The stern light, rear-facing, is also white and visible for 2 nautical miles. It can be directional or a 360-degree, all-around light.