All vessels are required to display what when anchored or moored?

When a vessel is anchored or moored, it is required to display a white light that is visible from all directions. This regulation is crucial for safety on the water, as it helps ensure that other boaters can see the anchored vessel, especially during the night or in low-visibility conditions. The white light serves as a warning signal to prevent collisions and accidents by making the vessel identifiable to passing boats.

In contrast, a red light is typically used to indicate the port side of a vessel when underway, and a blue light can signify various operational or emergency situations—neither fulfills the requirement for visibility while moored. The option indicating no lights required does not comply with safety regulations, as vessels must take precautions to be visible to protect both themselves and other waterway users. Thus, displaying a white light when anchored or moored is a critical safety measure mandated by navigation rules.