And, to any Navy or ex Navy folks out there, is COMINT tactical or support?
Tl;dr: That might be a Star Trek distinction, but it's not a navy distinction. But we're talking about two different things.
So...
My experience is almost 30 years past at this point, but I think it still mostly applies. At least in the US Navy, what Uhura did would be completely separate from signals intelligence gathering. One is communicating effectively with friends, the other is eavesdropping on the enemy. The signals/crypto/electronic/cyber intel stuff is done in secure spaces that require a security clearance to enter and is not talked about, and I still don't talk about it.
Aboard ship, "tactical" vs. "support" is not really a distinction that means much. At battle stations, everybody is in the fight. Traditionally, signals and radio communications was a "line" department, that is, the communications officer was in line to take command of the vessel if needed. Because it was vital to controlling ships in battle, it was often considered one of the more "elite" departments (even more so in the British navy). But all departments on a ship except supply and medical are headed by a line officer.
Navy cryptology officers, OTOH, are restricted line officers, who can't ever take command of a vessel at sea. It is a much smaller community of officers. "Back in the day," some entered directly as college grads, some transferred over from the line, but many, AFAIK the majority, were Limited Duty Officers who came up from enlisted Cryptologic Technicians (the "spooks"). These were very smart, impressive officers BTW. There were very few jobs for them at the rank of commander and above, though. This mostly still applies, I believe, though more positions may have opened up with the emphasis on cyber warfare.
At the time TOS was made, signal exploitation was limited to shore installations, or specialized undercover "spy" ships (like USS
Pueblo). It also was very much unknown, its origins with WW2 navy codebreaking was only beginning to become public knowledge. As the equipment got smaller in the '70s and '80s, that mission began to move on to regular warships. It became a small division under the Operations Department. The Ops Boss, of course, was a line officer. A large vessel like a carrier might have a crypto officer running the division, but on a CG or DDG just a chief of first class CT. Also, on a smaller ship Communications and Crypto might both be part of the Ops department, but again, completely separate. Now, I think, Commo is part of the Combat Systems department (and Radiomen now Information Systems Technicians), and Crypto, or whatever they call it now, is under Ops. One thing that might be confusing is that the
division with the CTs is usually the OS division (S for security), while sailors whose
rating is OS (Operations Specialist, radar systems) are in the OI division (I for Information, from the Combat Information Center).
The only time I can think of when something along those lines was mentioned was in "Balance of Terror," when Uhura said "cryptography" was working deciphering a message.
Was yellowgoldERRRRRgreen really tactical, though, or was that a TNG-era supplementation (for red and gold as changed)? I thought Sulu and Chekov wore gold because they were command-track officers, and De Salle and Hansen too.
The uniform colors seem to show the division of the ship where one is currently assigned, and no more than that. No "track" or larger career implications. Besides the obvious example of Spock, Scotty clearly has training to take command the ship and does so very effectively, and Lt. De Salle came up from engineering, in red, to take command.
This does beg the question, what ARE gold shirt jobs? Phaser control, helm, navigation, shuttle pilot? Anything else? They do seem to be jobs that everyone is trained to do. Landing party supervision maybe?
Ship and weapons control seems to be the bulk of it. I have said before, if it had been called the "control" division some confusion might have been averted, as a commanding officer seems to be able to come from any of the divisions.