I don’t suppose this answer is going to be helpful…

I enlisted in 1960, and we didn’t have to know any that I recall. And, if we did, they showed them to us in class, gave us a test, and I promptly forgot them.

Furthermore, I was in the navy 25 years, four and change enlisted and 20 and change commissioned. I never had to compose a message nor read a message sent by flags.

There are flags for letters and numbers. There are number pennants. Flags can also mean words, and some complete thoughts. There was a red flag that was called the "powder rag," that meant somebody was handling ordnance and it would be prudent to stay clear… I looked it up and found it’s the "Bravo" flag. But, whatever it’s called, I’ve seen it a few times… and know its intent.

Used to be a rating (Navy specialty) called "signalman" (SM). These were the guys trained to quickly compose messages and run up the flags and pennants. The skipper or watch officer would want a message sent, he’d call his SM. I have no idea who he’d call today. I know they still use flags, but they probably have some high-tech system that’s impervious to hacking and misinterpretation. If that’s the case, you probably don’t need to know any of them.