It is actually yellow. We do not have race committee, soooo the procedure is for the first boat that reaches one of the race marks can, if conditions warrant, shorten course by sounding a horn or a whistle and hanging the yeller flag off of their boom or stay.

Example: Wind from the North at 12, course is Start line to "P" mark to G5, five times to "P" mark to finish line. 45 minutes after start, wind drops to 4. Three laps have been completed by lead boat, so the lead boats shortens course as they round "P" mark. The finish line then becomes the goal for each boat after they have rounded “P” mark for the third time.