Every powerboat under 65 ft running at night shows three lights. They tell other boats where you are and which way you're heading. Watch each one light up in turn.

Small boats often use a single bi-color bow light (combo). Larger boats use separate sidelights on port and starboard. Both are USCG-compliant and produce the same 360° coverage pattern.

Another boat is approaching from your port (left) side — you can see their starboard (green) light. You're the stand-on vessel. Hold your course and speed. The other boat must slow down or stop and let you pass.

Another boat is approaching from your starboard (right) side — you can see their port (red) light. You're the give-way vessel. Slow down, alter course, or stop. Let them pass in front of you.

Two boats approaching head-on at night both see red + green on each other. Neither has right of way. Both vessels slow down and turn to starboard (right), then continue, passing each other port-to-port — the universal rule.