I think sticking with one style of TMP uniform for duty, and one for dress would have been better and then all other variants could have been off-duty wear.
It's a good point, people live on the ship as well as work there so a wider variety for off-duty is understandable. Chief Di Falco, for instance, is wearing a uniform with no rank insignia, which makes sense if it was an off-duty uniform and she was off watch and called to the bridge in a hurry.
I have to correct my own earlier post as I actually looked in a book instead of relying on memory. According to TMoSTTMP, the two-pieces with sleeve rank was "Class A," a little more formal duty uniform presumably worn "in port," and the two-piece with shoulder rank was "Class B," the normal dress for duty underway and available in long- and short-sleeve versions. The one-piece jumpsuit with shoulder rank and cargo pockets was working dress.
Spikes page breaks it down as
Command officers-Blue
Bridge officers-Beige
Non-bridge personnel-Brown
Technicians-White
Planetary personnel-Gray
That's pretty much the "official" breakdown, I think, but in-universe there are so many exceptions to it that it must either be incorrect or somewhat meaningless.