Lighthouses are most well known for alerting sailors to hazards and coastlines during the night, or through conditions which impeed visibilty, such as rain and fog. However, lighthouses also help to mark the coast by day.

A system developed by the Lighthouse Board (est. 1852 by U.S. Congress) designated individual lighthouses as "daymarks" by the use of painted patterns. Unique patterns painted on lighthouses enable sailors to recognize them as markers for particular locations during the day. Although many lighthouses are painted with similiar patterns, they are far enough apart to prevent them from being confused with one another.

Some lighthouses have simple bands of color, others are painted with spiraling lines and still others are painted one solid color. The most common colors used to paint lighthouses are white, black and red.
A few lighthouses notable for their markings include:
 
Bodie Island Light (Nags Head, NC)
three white and two black horizontal bands
Cape Bonavista Light (Bonavista, Newfoundland, Canada)
white with vertical red stripes from top to bottom
Cape Hatteras Light (Outer Banks, NC)
a black spiral against a white background
Cape Henry Light (Chesapeake Bay, VA)
long, vertical black and white checkerboard pattern
Cape Lookout Light (Cape Lookout National Seashore, NC)
large black and white diamond pattern
West Quoddy Head Light (Lubec, ME)
eight thin, horizontal red stripes against a white background

 
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Marking the Lights ...distinguishing colors and patterns