Greens are usually "Can" Buoys, and Reds are usually "Nun" Buoys. There are different Buoyage systems used through the world. Here in the US a Channel usually has a Red and white buoy (Morse A as an Light Identifier) marking the beginning of the channel, and then green buoys port side (going in) and red ones (Red right return).
Maybe someone should make all the different buoy types and offer them up for use in a upcoming new Naval Sim...???
Buoys are easy, however there sure are a lot of the buggers...
http://www.boatwashington.org/navigation_aids.htm
Cheers
Beer
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