As old timers like me would say, the addition of the gold squares and triangles to ICW markers years ago was the best thing since sliced bread! They really assist at intersections where multiple sets of marks may occur. It’s hard to believe, but sadly true, that there are ICW boaters who have never noticed the small squares and triangles. Captain Adams does an excellent job of explaining their meaning and their use.

Here are my thoughts on the spectacular grounding in Georgia. First, if the chart plotter was working properly I doubt that the chart plotter was in error. I’m not sure that a lot of people understand that the markers and buoys in the ICW are dual purpose. on each of the ICW markers or buoys you will see either a yellow triangle or a yellow square and it doesn’t matter if the marker or buoy is red or green. When traveling from say Boston, Mass. to Brownsville, Texas you would keep the marker with the yellow triangle on your starboard side and the yellow square on your port side for the entire trip, and do just the opposite when traveling the reverse direction. A lot of people say that when going south keep the yellow triangle on the starboard side. However, when traveling south on the West Coast of Florida this would put you out of the channel. Rather than to use north or south I like to use the terms `Land side (yellow triangle)’ or Sea side (yellow square)’. One last thing I would like to point out is that traveling the ICW going through Georgia and South Carolina, the Red and Green markers swap sides in the channel depending on which inlet you are passing (going in either direction) so red right returning is not really true if you are relying on that old saying. You have to pay attention to the Yellow symbol on the marker to determine which side to pass on and all of the electronic charts I have ever used have always been right on. I can’t tell in the picture if the yellow indicator is a square or triangle but it has to be a yellow square if you would pass to the east as indicated by the boater who passed by. So my guess is that this was an operator error.
I see this happen a lot where people with a lot of money go out and buy a big fast boat without any experience or navigational knowledge (there are hundreds of Sea Ray stories). They are told to keep the red markers on their right side and sometimes this is what happens, so it’s obviously the chart plotters fault since they kept the red marker on their right side. Use your electronics as a tool not a rule and reference your paper charts often and plan in advance. Keep your eyes ahead and stay alert, and when in doubt, slow down and assess the situation.
John Adams, Captain, USCG Master aboard MV Ithaca

Seems that your explanation is a convulated way of saying that red marks are triangular and green marks are square. The reflective gold marks are also triangular and square so that you may ascertain the shape in the dark.
I too teach my students, GREEN TO SEA. Thus, they are able to ascertain which color is on which side.
Yes, many inlets intersect the ICW and can cause confusion; St. Augustine comes to mind.
Capt. Guy

The idea that the `yellow’ marks identify the ICW is simply not totally true. They are used on all Federal Waterways. North bound on the ICW arriving in Stuart has 2 #2 markers (with yellow symbols) close to each other. They should be passed to your port northbound. If you are heading west on the Okeechobee waterway to cross the big `O’ you will find a red marker #2 with a yellow mark that must be taken to your starboard. It is only 200 yds from the other #2 (complete with yellow symbols). Don’t take my word for it. Check it out your self and be very careful when Federal Waterways intersect.
Captain Ed Potter