Okay, so I'm no expert on Trek tunics, but do have a few insights that will hopefully assist in the recreation of thinking...
(Dang this is a long forum to catch up on.)
Rod.com should have the most accurate available braid and insignias from the access Majel had to materials used in the productions. Now, having said that, JoeK also had great access to Trek and Western Costume and should also have good replicas.
Joe and friends are now working on their own fan productions with him as captain of the Excelsior (a la New Voyages.) Yet I digress...
Bill Theiss was well known for custom making things and also finding very obscure fabrics from arund the world.
For example, the Romulan costumes seen in 1st season TNG were fabric he had picked up in France many. many years before. That's why, later in the series there was no more of it and Romulans wore similar but different patterns.
Also, the virtually every piece of fabric used on Next Gen was custom colored. I would expect that the TOS wardrobe was as well, since they wanteed bright vivid colors to help sell color television sets.
Bill also used hidden zippers whenever he could and always strove for unique textures so that fabrics wouldn't look like 20th century Earth.
The original uniforms for TOS were in a room above TNG wardrobe up until about a month after Enterprise was cancelled.
They had access to many examples for the DS9 episode and I suspect the principle differences you see in color are strictly due to lighting, camera and film technology and the differences between Jerry Finnerman and Marvin Rush as cinematographers. Now Marvin is a fanatic and no doubt did whatever he could to replicate the TOS lighting but the whole process was different by then (negative, transferred to digital video, edited and then printed to film.)
Also remember that the Original Series had virtually zero budget. Wardrobe was always recycled and if someone was cast and not able to make a fitting, it was fit onto a "double" as best as they could. Also sometimes decisions are/were made at the last minute and a different uniform would be grabbed if it fir better with artistic license taking a back seat (engineering lieutnenant in ensign sciences uniform, for example - probably all they had that fit and no time (=money) for changes.
A short story about the wrap arounds (maybe you have heard a million times already...):
Bill (Theiss) created the green wrap around for Shatner because he had a "high ribcage" and Theiss felt that it made him look fat, when he wasn't (talking early here.) He knew that the diagonal line would help disguise this and so created the alternate captain's uniform.
I fear that if I got one of these nowadays, I'd need a much larger diagonal line...
Oh yeah, and Bill (T) called the Tholian costumes "Penis suits."
My experience is more recent then TOS but hopefully I can help shed some light on some of these things, if/when possible.
The screen caps are fantastic, people here certainly have good eyes for the details.
I wanted a "Spock shirt" so badly as a child - until my mom told me they were velour, which was way too hot for me to ever wear.
So, she sewed a (Lincoln Enterprises) captain's insignia onto my wallet, which I could flip open like a communicator. :rolleyes