There were three uniform variations of the TNG skants that I came across during my costume research.
The first, I already mentioned – for their infrequent season two appearances, costume designer Durinda Rice Wood added corresponding black trousers to the TNG skants.
Here’s an auction photo of a pair of season two uniform trousers, incorrectly paired with a later TNG-era admiral uniform.
In this listing photo, we can see that these trousers appear to have been jumbo spandex (which makes sense) and have division-colored lower front accents analogous to those on the corresponding TNG jumpsuits.
"All Good Things ..."
The second uniform variation was actually a physical modification of the TNG skant itself, by costume designer Robert Blackman for the series finale.
From season three to the end of the show, Blackman had many monumental tasks and issues to address – updating an entire production’s worth of uniforms, charting “The Lost Era” uniform timeline to reconcile others’ radically different uniform designs, generally expanding the Starfleet uniform family, creating alternate uniforms for other realities/timelines/etc., establishing the wardrobe of recurring alien cultures, and of course the ongoing “aliens of the week” – but he’d never actually had to deal with William Ware Theiss’ TNG skants.
When The Next Generation’s final episode came around, though, one can imagine Blackman frenziedly going through whatever unmodified early TNG-era uniforms were still in storage and available for use, and reading through any notes William Ware Theiss might’ve happened to leave behind on the TNG skants (if there even were any) …
Keeping in mind that Blackman only had a brief time in which to prepare an entire line of early TNG-era uniforms, create a brand-new design for the “alternate future” uniforms so his department could whip up potentially dozens of them for the last episode, design all the civilian costumes for the cast’s older selves, and incorporate other existing elements like Q’s “judge” costume … it should come as no surprise that Blackman simplified the construction of Counselor Troi’s TNG skant a bit for the finale.
(The extras appear to have worn Theiss’ existing TNG skants from the first season.)
At a glance, one might assume that the costume department had simply pulled Deanna’s original uniform out of storage for the final episode, but in actuality, it appears to have been a modified design and custom-made uniform.
Specifically, Blackman appears to have done away with the front double-zipper closure and instead had the skant simply zip closed up the back.
Comparing the upper front areas of her uniforms from the pilot and finale, one can easily observe how the zipper areas were somewhat wrinkly on the former, whereas the same seam lines were noticeably smoother and “cleaner” on the latter.
Obviously, dressing Counselor Troi in the TNG skant made perfect sense considering the episode’s setting and events, and only eagle-eyed viewers would notice so subtle a difference, even in remastered HD.
But the question arises as to why she didn’t simply wear the same uniform from the pilot (and by extension, why this uniform variant even exists) …, and we can only speculate.
Perhaps the original pilot skant(s) had been subsequently lost, ruined, or were otherwise unavailable or unusable.
Maybe the original skant(s) no longer fit Marina Sirtis, so she needed a new uniform made for the finale.
Or maybe it was simply due to the teal fabric color itself; the season one teal was a far cry from the season seven teal (see below), and Blackman may have wanted the division colors to seem more homogenous over the timeline transitions.
It could’ve been for any combination of these reasons, or for other reasons entirely.
Original Wardrobe Test
This third uniform technically isn’t “canon” since it never appeared in an episode, but I do believe it worth mentioning.
In an original wardrobe/makeup test (as seen on the TNG season 1 Blu-Ray set), Marina Sirtis wore a TNG skant that was a bit different than those we’ve looked at thus far.
Specifically, this earlier prototype of the TNG skant may have had a different style of zipper closure, and it also appears to have been topstitched across the upper front of the division-colored panel.