What color light does a special mark buoy exhibit at night?

A special mark buoy is used to indicate a specific area or feature that does not fall under the typical navigational aids, such as safe passage or danger. According to the IALA Maritime Buoyage System, special marks are designated to be yellow in color. At night, these buoys exhibit a yellow light, making it distinct from other navigational signals.

The yellow light helps mariners recognize these buoys as indicating an area of interest that should be noted, such as subsea cables or other underwater constructions, ensuring safe navigation around these features. This characteristic makes yellow the correct answer when identifying the light color for special mark buoys during nighttime.