(1) Lights on aids to navigation are differentiated by color and rhythm. Lighthouses and range lights may display distinctive light characteristics to facilitate recognition. No special significance should be attached to the color or rhythm of such lights. Other lighted aids to navigation employ light characteristics to convey additional information.

(2) When proceeding in the conventional direction of buoyage, aids to navigation, if lighted, display light characteristics as follows:

(a) Green lights mark port (left) sides of channels and locations of wrecks or obstructions which are to be passed by keeping these lights on the port (left) hand of a vessel. Green lights are also used on preferred channel marks where the topmost band is green.

(b) Red lights mark starboard (right) sides of channels and locations of wrecks or obstructions which are to be passed by keeping these lights on the starboard (right) hand of a vessel. Red lights are also used on preferred channel marks where the topmost band is red.

(3) The purpose of aids exhibiting white or yellow lights may be determined by their shape, color, letters or numbers, and the light rhythm employed.

(4) Light rhythms, are employed as follows:

(a) Aids with lateral significance display regularly flashing or regularly occulting light rhythms. Ordinarily, flashing lights (frequency not exceeding thirty flashes per minute) will be used.

(b) Preferred channel marks display a composite group flashing light rhythm (groups of two flashes followed by one flash).

(c) Safe water marks display a white morse code "A" rhythm (short-long flash).

(d) Isolated danger marks display a white group flashing two.

(e) Special marks display yellow lights with fixed or slow flashing rhythm preferred.

(f) Mooring buoys and information and regulatory marks display white lights of various rhythms.

(g) For situations where lights require a distinct cautionary significance, as at sharp turns, sudden channel constrictions, wrecks, or obstructions, a quick flashing light rhythm (sixty flashes per minute) may be used.

(h) Occasionally lights use sectors to mark shoals or warn mariners of other dangers. Lights so equipped show one color from most directions and a different color or colors over definite arcs of the horizon as indicated on the appropriate nautical chart. These sectors provide approximate bearing information since the observer should note a change of color as the boundary between the sectors is crossed. As sector bearings are not precise, they should be considered a warning only and not used to determine exact bearing to the light.