Which type of marking is used for caution in navigational aids?

The solid yellow marking is specifically used to indicate caution in navigational aids. This color is universally recognized as a sign to alert mariners to proceed with care, often indicating areas where navigational hazards may be present or where specific caution is required. For instance, solid yellow markings can be found on buoys or other aids to navigation that guide vessels through areas of increased risk, such as shallow waters or regions with potential obstructions.

In contrast, other markings serve different purposes. Flashing white markings are typically used for safe water areas, while alternating red and green is indicative of safe passage or channel markers—guiding mariners safely along established routes. Flashing blue markings are not commonly used in navigational aids. Each marking color has a specific meaning, contributing to the overall safety and efficiency of maritime navigation. Thus, solid yellow stands out specifically for its role in signaling caution.