Which type of buoy may exhibit yellow lights?

The correct answer is that special purpose buoys may exhibit yellow lights. Special purpose buoys are distinct from other types of buoys because they are utilized for specific functions that don't fall under conventional navigation aids. This includes marking underwater obstructions, designated fishing areas, or other areas of particular interest. The use of yellow lights on these buoys serves to alert mariners to their unique purpose and differentiate them from standard navigational markers, which usually use white or green lights.

In contrast, vertically stripped buoys typically utilize colors and lighting that align with specific navigational information, such as marking safe water or channel entries but do not specifically indicate a special function through yellow lights. Horizontally banded buoys and spherical buoys similarly conform to navigational conventions set forth by regulations and do not typically present yellow lights as part of their standard operating procedure. Hence, the identification of yellow lights with special purpose buoys effectively signifies their designated role in the marine navigation system.