What additional lights may be shown at the top of the mast on a sailing boat greater than 7 metres?

The additional lights that may be shown at the top of the mast on a sailing boat greater than 7 meters are two all-round lights arranged in a vertical line, specifically red over green. This combination indicates that the vessel is under sail and has the capability to be powered, but is primarily sailing. The red light indicates that the boat is still a sailing vessel at the top, while the green light below signifies that it is sailing or showing its status as a powered vessel if necessary.

This lighting configuration is crucial for distinguishing the type of vessel during nighttime or poor visibility conditions. It helps other vessels to identify the navigation status of the sailing boat, promoting safety on the water. The use of red over green is a standard marking in maritime navigation to ensure clarity and compliance with the International Regulations for Preventing Collisions at Sea (COLREGs), which aim to prevent maritime accidents.