Red sectors of navigation lights are primarily used to warn mariners of what?

Red sectors of navigation lights are primarily used to warn mariners of hazards such as shoals or nearby land. When a navigational light shows a red sector, it indicates that mariners should exercise caution as they are approaching a dangerous area where the depth of water is insufficient for safe navigation. This signaling helps prevent grounding or collisions, emphasizing the importance of understanding the graphical representation of lights on nautical charts.

In this context, the specific use of red indicates a danger related to navigational safety, making it crucial for mariners to heed these warnings as they navigate through potentially hazardous areas. Understanding the function of these color-coded sectors enhances mariners' situational awareness and is vital for safe passage.