I am intimately familiar with the Rules of the Road anchoring light requirements as put forth in COLREGS concerning white light(s) and deck lighting based on vessel length. However, I was recently in St Martin and I saw a lot of large yachts, both in slips and at anchor, with red lights atop their masts. I should add that the masts were the kind with many spreaders and with spreader lighhts so the whole mast was basically lighted. Maybe that might have some effect on this situation.

One fellow told me in International Rules this was required for masts of over 150' to ward off airplanes, similar to a cell tower. Makes sense but I can find no Rules reference to this and wondered if anyone knew about this and where it was stated? It was suggested that this might be in the British Rule book, but I thought International meant just that... International.