The red-over-green configuration has several obvious advantages: it says unambiguously that: "this is a sailboat." While other sailors and recreational motorboat operators may not be familiar with the configuration, those who have taken the OUPV and Master courses for a CG license will have spent literally hours studying the various lighting configurations. The operators of the Big Boats (the ones where my boat would only leave an insignificant smudge on their hulls) should know what red-over-green signifies.
What's good about the red-over-green light configuration is this: a sailboat with only deck lights will display only one (red, green or white) light down on the water. In swells, those lights intermittently vanish behind the swells. A tri-color masthead light alleviates the problem of vanishing behind swells (unless you're sailing in The Perfect Storm conditions). But... neither of those configurations says: "This Is A Sailboat." In dark conditions, the helmsman of another vessel can't see your sails, and consequently has no reason to give way when all he can see is a lonely green light against the dark waters (and if he can presume you're motorsailing, he still has an excuse for not giving way - legally you're a motor vessel when "propelled by machinery").
With a red-over-green configuration, you can run your nav lights down on the deck simultaneously
with the red-over-green lights. This gives "aspect" information AND identifies you as a sailboat.
Trying to implement the lights with a commercially built solution is frustrating. Nobody makes the correct configuration of lights. Adding to the frustration are the requirements: an all-around red light over an all-around green light at or near the top of the mast (COLREGs Rule 25(c)), with the lights separated by at least one meter vertically for vessels 20 meters and less, or two meters for vessels over 20 meters (stated in Annex 1 of the COLREGs)*. If you look in your COLREGs book under Rules 25(c)
you will see an impossible depiction: the only way those lights would project over all 32 points (360 degrees horizontally) is if both
the mast and
the sails were transparent
! Otherwise, over most of the horizontal arc, another vessel would see only the red light on top. (The fact that no boat I've ever seen has its spreader that far up the mast as depicted also implies the artist knew nothing about sailboats).
So, my solution, a DIY red-over-green light. I took 55 inches of 1 inch ID PVC pipe, installed 24 red and 24 green LEDS one meter apart, and mounted that to the top of my mast. I also installed a relay to turn the lights off when my masthead light is on. The masthead light, by the way, is mounted on the same PVC pipe... at the mast head
- so it's a real masthead light... not a half-way-up-the-mast light. The rules specify a minimum
height - not a maximum height for that light. The purpose of a masthead light is to be visible at a distance from ahead, abeam, and two points abaft the beam either side (20 points/225 degrees total)-- when otherwise your operation without sails (under power) would make your sailboat nearly invisible. The higher the light is above the water, the greater the visible distance to other vessels.
There are a few other refinements to my DIY lights - like voltage regulators, and transient and RF suppression, but that's the crux of my implementation.
While there is an exception in the COLREGs that allow use of two lights on either side of the mast that would get around the problem of finding a transparent mast, it won't solve the problem of obscuring the green lights by the non-transparent sails -- and the total cost is over $600 for 4 decent commercial light assemblies. My solution cost $75: LEDs, circuitry, and PVC pipe all combined.
*§ 84.03 "Vertical positioning and spacing of lights", paragraph i.