What does a yellow light signify when attached to a vessel?

A yellow light attached to a vessel specifically signifies a towing light. This light is used to indicate that the vessel is engaged in towing operations, which is crucial for the safety and awareness of other vessels in the vicinity. The towing light helps to communicate the nature of the vessel's activity, allowing other mariners to understand that the vessel is not only navigating normally but is also towing another vessel or object, which may restrict its maneuverability.

In maritime navigation, distinguishing between different types of lights is essential for safe navigation and avoiding collisions. For instance, the masthead light typically signifies the presence of a vessel underway and is white, while the sternlight is also white and typically indicates the back of the vessel. An ahead light generally helps signify the direction a vessel is moving, and it would again be white for most purposes. Thus, recognizing the color and type of light helps operators adhere to the COLREGs, enhancing maritime safety.