Buoys are floating aids to navigation used to mark channels and warn of
dangers such as shoals or obstructions. On the chart, lighted buoys are
indicated by a purple flare from the buoy symbol or by a small purple disk
centered on the position circle.
Buoys are distinguished by color, shape, topmark, lights, and sounds.
The colors red and green are used for lateral marks or to delineate the
edge of a channel. These can be colored all red or all green, but they
can also be horizontally banded red and green or vertically banded red
Yellow is reserved for special buoys which may be used to indicate an
unusual area or feature such as traffic separation, spoil ground, military
exercise zone, cable, pipeline, or recreation zone.
When you shine a searchlight on buoys at night, reflective tape helps
identify them, and the color of the reflective material agrees with the
color of the buoy.