What should be observed if a vessel wants to use the preferred channel?

The top color of the mark is crucial when determining the preferred channel in the IALA Maritime Buoyage System. This system uses a color-coding method whereby the color of the top part of a buoy directly indicates the side of the channel or navigational aid that is preferred when navigating.

For example, in the region A of the IALA system, a buoy with a top color of red generally indicates that vessels should keep that buoy on their port side when entering a channel. Conversely, if a vessel approaches and sees a buoy with a top color of green, it signifies that the vessel should keep that buoy to starboard. Understanding and following these color indicators helps ensure safe navigation, as they communicate critical information about the channel to mariners.

While other factors, such as bottom color, preferred channel markings, or light color, can contribute to understanding navigation, the top color specifically indicates the direction a vessel should take relative to buoys marking the channel. This makes it essential for mariners to observe the top color of navigational marks when determining their path through channels.