Tricolor vs. Red-Over-Green + Sidelights

 A sailboat needs to show red and green sidelights when sailing (no all-around white, as when motoring).

Boats under 20 meters can substitute a tricolor at the top of the mast. (Not a masthead light BTW--that is a steaming light located on the front of the mast, AKA a steaming light. A confusing matter of COLREGS definitions.) The primary advantage when the rule came out is that fewer bulbs and fewer amps were required. Additionally, it can be more visible in waves.

 

 

Another option is red-over-green, which can be used on any size boat. It may not be used in combination with a tri-color, probably because it could be confused with certain task light combinations (restricted ability to maneuver, underwater operations, dredging) from certain angles and in poor conditions. It is the only high location that can be used by larger sailing vessels, so many believe it is only for over 20 meters or that it is required over 20 meters, but neither is true.

 

 

Notice that in the COLREGS illustration the green light will be reflect of the sails and will be obscured in some sectors. Since it is supplemental, I guess the latter is considered non-critical. It would be a minor arc of the genoa. The reflection off the sail might be quite annoying. But the blocked sectors could be large, about 120 degrees, where as 6 degrees is the COLREGS limit for other lights, such as anchor lights.