What color must a flashing light be, according to the navigation rules?

The requirement for a flashing light to be white is established in the navigation rules to ensure visibility and recognition for all types of vessels. The white light is used specifically to indicate the presence of a vessel that is underway and can help in signaling to others on the water, especially at night or in conditions of reduced visibility.

Flashing white lights are often employed in specific situations, such as indicating a vessel that is engaged in certain activities or is restricted in its ability to maneuver. This standardization helps mariners quickly identify the status and intentions of other vessels, thereby enhancing safety on the water.

While there are other colors such as red and green that may indicate different things in maritime navigation (for instance, red typically indicates a port side and green indicates starboard, according to buoyage systems), the rules specifically require that a flashing light used for signaling must be white to convey the necessary information clearly and effectively.