If a vessel wishes to use a secondary channel, which colour should be observed?

In the IALA Maritime Buoyage System, a secondary channel is typically marked using green buoys. The presence of a green buoy indicates that the channel is navigable and directs vessels towards the preferred route, especially in two-way traffic situations. The green color is standardized to represent starboard side guidance when returning from open water. Therefore, if a vessel wishes to navigate through a secondary channel, observing green buoys is crucial.

The other color options are designated for different purposes within the buoyage system. Red marks are used to indicate the port side of the channel when returning from the sea, while white and black might not provide the necessary navigational information pertaining to the channel. Understanding this color code is essential for safe navigation and for making informed decisions while navigating through designated water routes.