Red and Green Light on a Boat

By Matt Claiborne

So, which side has the green and which is red? And what color is a boat’s sternlight?

The green light is on the vessel’s starboard side, and the red light is on the vessel’s port side. The white light is on the stern, or back, of the vessel.

But it’s a little more complicated than that. For example, precisely how many degrees the color of light shines is standardized.

So if you are putting a red and green combination light on your boat, you must ensure that it meets USCG standards and shows the correct field of view.

The red and green lights are visible from dead ahead to 122.5 degrees back on each side.

Combination lights on the bow are common on smaller boats. They make both red and green lights with a single bulb and have the appropriate viewing angles.

Larger vessels have two bulbs, called sidelights, that are mounted apart. They also have a masthead light, a white light shines forward.

And finally, a white stern light pointed aft. A Sailing vessel under sail does not need the forward masthead light, but they need to turn it on when under power.