What color signal indicates a vessel that is sailing if it is powered by machinery?

The color signal that indicates a vessel which is sailing and powered by machinery is indeed red over green. This signal is part of the navigation lights system used to communicate a vessel's status to others on the water. Specifically, red over green indicates that a vessel is under power with a sailing status, meaning it is both sailing and using its machinery, which distinguishes it from a vessel that is purely sailing under sail without any mechanical assistance.

Understanding this signaling is crucial for ensuring safe navigation. Vessels need to communicate their intention and capabilities clearly to avoid collisions and ensure that other mariners can respond appropriately to their movement. Each combination of lights has specific meanings, creating a standardized language for water traffic.

This particular signal helps other vessels or those at anchor to recognize the maneuverability and the actions of the vessel displaying the lights. Red over green serves as a visual cue for other operators on the water, indicating both the type of vessel and the presence of propulsion power, which informs the actions that others might take when encountering such vessels.