What do the red, green, and white navigation lights indicate on a vessel underway at night?

• A. Red = port, Green = starboard, White = stern; additional white masthead lights indicate forward travel.
• B. Red = starboard, Green = port, White = bow; masthead lights indicate backward travel.
• C. Red = stern, Green = bow, White = all-round white; masthead lights indicate mooring.
• D. Red = port, Green = starboard, White = stern; masthead lights indicate stationary.

Answer: (A)

The main idea is how to read night navigation lights to tell a vessel’s orientation and motion. On a vessel underway at night, the red light marks the left side (port) and the green light marks the right side (starboard). A white light at the stern is visible from behind. If the vessel has forward white masthead lights, these indicate forward travel and that the vessel is moving ahead. So the standard arrangement—red on port, green on starboard, white stern light, plus forward white masthead lights when underway—is what you’re looking for. The other descriptions mix up which side is red or green, or conflate bow/stern or mooring/stationary scenarios, which isn’t correct for a vessel actively moving at night.