Someone above mentioned "us" against "them".
I missed service, (deigned on a medical in the 80's) but my trade is electronics and computers, so I work with LOTS of ex-service people.
"us" against "them" is a natural condition in and out of the service. If anything, the rivalry between the branches drives the differences in uniforms as much as anything else.
In the future as jobs get ever more specialized, there will be even more of that sort of thing.
To make a starship run, each department will come to believe that they are the KEY to keeping the ship running. For example, regular crew would likely not be ALLOWED, in engendering spaces, and officers might only be tolerated, within limits. Same for life support, nav. and flight crew, gunnery, and of course the small craft crews and mechanics will defend themselves by adopting there own identifying gear. You guys from the service remember how much first watch and third watch, IN THE SAME DEPARTMENT, manning the same stations resent each other, now take 5700 YEARS of tradition to build, and tell me different departments are not going to DEMAND a way to tell each other apart by uniform.
I would think color-coding, or some other system that says, "Hey, I BELONG to the drive section" would be a natural progression.
And the discussion of flight crews goes even stronger for people in vacc suits. With out facial features, or even general build, and all comm. by radio, PLUS the most hazardous environment imaginable, any crew over 3 or 4 is going to NEED real clear visual clues to know who is who. Otherwise fatal mistakes in ID become way to difficult to avoid. Even inside the ship, working on the engines say, looking a couple of hundred meters across the deck to see who just came through the hatch, color and VERY BIG markings are the only clues you will have who the guy that just crawled through the hatch is. Is it your partner coming back with the jump grid depolarizer you need, the chief coming to see why you are taking so long, or that pesky quartermaster coming back to tell you one more time why you can’t get your replacement parts, ‘cuase you didn’t get the right chiefs signature and thumb print in the right box.
Just my .02cr, but it seems to be the way things get when tradition builds up long enough, and the third imperium is driven by ritual and tradition.
On the other hand, I agree that the style is going to be as utilitarian as possible, at least in the “working” departments. Drives, power, life support, avionics, computers, all of those crew. Flight crew, Nav, flight systems, comm. scanners, don’t have quite the need to pack tools with them wherever they go, and duty uniforms might be a little more dressy.
Personally, only my opinion, and my TU, but I always thought of dress uniforms as elaborate in the extreme. Again after ages of tradition, elaborate uniforms that are difficult to make all of various epaulettes and cravats and other adornments hang just right would be just the thing to show the planet-siders just what spit and polish it takes to be a REAL MAN( or woman for that matter) and travel the stars. Army will try to out shine the NAVY, ‘cause you know the ground pounders HAVE to show up those Nave pukes that think setting in a chair pushing buttons is work, and Jar heads, well they are just going to be jar heads and have to out do everybody, just to prove their not really jar-heads. (Sorry, my old man was a swabbie, and I was signed for 6 for reactors on subs, so my own service biases are shining though. NO intent to insult ANYONE that has served their duty, but the service folks all know how one branch feels about another.)
Then of course there are the merchants. Their dockside dress uniform HAS to make them look prosperous, hence elaborate, and expensive, if they have any hope of drawing business. Subsidizes merchants probably won’t wear dress often, but I bet you, the tramps and the free traders are going to look like clowns trying to be walking billboards. And crew probably won’t be allowed off ship with their best dockside gear on. Got to look PRO-FESS-ION-AL like to impress the passengers and the mercantile exchanges.
Anyway, my thoughts.
Mr TEK