It doesn't quite fit the Institute theme, but I'm partial to using the clean Postman outfit & hat for my supply line folks.
Using your current system, I would suggest also giving Courser uniforms to the provisioners as they also need to protect themselves. Alternately, synth armor (or put synth armor on your guards and courser uniforms on your provisioners).
Alternately don't put them in anything special -- they're going into the outside world and need to blend in, much like gen 3 synths.
If I did it, I would rework things, given that Institute lab coats come color-coded, I would use this and do things this way:
Farmers - Plain Institute jumpers
Merchants - Different colored Institute lab coats for different purposes: orange for general store, green for food/drink, black for weapons and armor, blue for clothing, red for medic. Division head if it's a tier 3 store.
Scavengers - Yellow Institute lab coats (yellow is engineering)
Guards: Courser uniforms
Provisioners: Clean Room suits.
I think to get enough suits you'd probably have to pickpocket/reverse pick pocket institute people but it could be doable.
Well, I must confess that on the PC I just used the console to add the Postman Uniform and Postman Hat to my inventory when needed...
player.additem 00146174 1
player.additem 001F9790 1
...respectively.
Women in Road Leathers. Men in harnesses.
Provisioners with combat shotguns (tricked out), guards with mini-guns, lasers and plasma rifles. All of them get molotavs and grenades.
Don't care about where they're working once I've assigned them. I figure, once I've assigned them a bed and a job, I put them in an outfit and that's how I know I never need to talk to them again.
And now I feel dumb. Really dumb. Which is why this is a such a great community.
It never even occurred to me to dress the settlers in uniforms so that I would know what their job is. This question has vexed me and the answer was right there in my face the whole time.
Not dumb at all!
These folks gave me the idea too. Gotta love 'em.
Sure it looks cleaner, but not nearly as kinky. Plus it's one of the few ways I ever found to actually make my settlers atractive. Of course that obviously says something about my S&M and leather fetishes.