Starfleet uniform (2250s-early 2270s)
This type of Starfleet uniform was used from around the mid-2250s to the early 2270s. The general tailoring of the "tunic and pants" uniform design worn by Starfleet service people was maintained throughout that period, but with changes in collar, rank insignia, and revised colors for Starfleet divisions and departments. () 

In the 2250s, a previous uniform design was also being used concurrently with this one at least until 2258. () 

Uniforms of the era were made of an organic, algae-derived fabric, xenylon. () Captain James T. Kirk once pointed out to an illusory inhabitant of the Melkot simulation of Tombstone, Arizona that Starfleet uniforms did not look like the illusion's clothing. () In addition, they had built-in temperature controls to accommodate for cold weather environments. For example, upon beaming down to the surface of Sigma Draconis VI, Captain Kirk instructed his landing party to set their "suit temperatures to 72(° Fahrenheit)." ()

These uniforms were drastically replaced in the 2270s, with a change of many uniform variants sometime after 2270. ()

Standard duty uniform

Type A
This uniform lasted from before 2254, to provisionally at least 2268. () 

This uniform was used by the crews of the , the Antares and officers visiting Deep Space Station K-7. () By 2265 it only saw occasional use and was for the most part replaced by newer variants. ()

The standard duty uniform consisted of dark gray or dark blue trousers and a division color top, following the below color code. The previous Earth Starfleet-style of wearing a patch based on assignment continued, but the patch was moved to the chest. Rank was displayed by sleeve stripes. () The top's collar was initially designed with a mock turtleneck appearance but many of them came straight up on the neck later on. ()

Female variant

Women's uniform style had a cowl neck collar and closed with a zipper down the back. They also wore black trousers similar to the male uniform. ()

Seamed variant

A variant worn by certain personnel included a closing seam radiating from the side of the neck. ()

Type B
This style, in use by 2259, is a simplified evolution of an earlier uniform variant. (; )

In 2265, the crew of the Enterprise abandoned this design to briefly revert to the 2254 version. ()

Variants
Some officers wore variant versions of the uniform with black tunic sides, sleeves and shoulders in addition to division colors. Additionally, officers of either gender could wear a skant version of the uniform. ()

Type C
 

This style is a further simplified evolution of the previous version. It was initially put into use on some starships by 2265, but other starship crews or individual service members continued to wear the older style until 2268.  (; ) 

As with earlier Starfleet uniforms, the divisions were distinguished by color, and were generally described as gold (or green) for command division, red for operations division (engineering/special services), and blue for the sciences division. (; ) 

Into the 24th century, scholars of Starfleet history will note the division colors of this era. Miles O'Brien and Benjamin Sisko told Julian Bashir of the different practices when, in posing as "contemporary" Starfleet officers during an unplanned visit to 2268, the doctor, admitting he was no historian, initially did not understand why the captain wore a "gold" uniform and the engineer a red one, as the uniforms of his career conformed to a different standard. ()

Epaulet

In 2254, dress uniforms of high-ranking Starfleet personnel contained a certain epaulet, likely indicative of rank. ()

Appendices

Appearances

Type A

Type B
  All episodes

Type C
  All episodes except:
 
 
  All episodes

Background information 
In the original pitch for the series, Gene Roddenberry generalized their design, stating "Crew uniforms are 'naval' in general appearance, attractively simplified and utilitarian. Again, surprise variations are possible here too."

The Starfleet uniforms worn during  were designed by William Ware Theiss, who returned to design the  uniforms (which were further adapted into future versions on , , and in the TNG-era films by Robert Blackman).

The "Type A" uniform was in use only for the two Star Trek pilots, with the tunics appearing in several later episodes (see above) and the matched pants having been worn by extras in several early first season episodes, with the new updated tunics.

Although the "Type C" command division uniform tunics looked gold on most color TV sets, the costumes were actually limeority.blogspot.com/2008/05/bill-theiss-lost-interview-rare.html] This issue was made light of in an in-joke from the first draft script of , in which Department of Temporal Investigations agents Dulmur and Lucsly – just prior to leaving space station Deep Space 9 – asked Benjamin Sisko one final question: what color had Kirk's uniform been. Sisko, having seen Kirk in both a duty uniform and wraparound tunic, simply answered, "Green." The greenish hue of the command tunics can be seen more clearly in the third season, when the fabric used for the tunics was changed from satin velour to a double-knit fabric that reflected the set lighting differently. The dress uniforms, made of a silk material, were always clearly green by comparison, and some darker green jumpsuits and wraparound tunics that were more clearly seen seemed to confirm that all the "gold-to-green" variations were part of the same color scheme. The so-called "beige" Type A uniforms which originated with  were ironically a much more yellow color, but likewise appeared beige or pinkish under the lights.

The Type C first appeared in . Chronologically, the Type C uniforms first appeared in late 2265 in the flashback scenes in  and the recording of Doctor Leonard McCoy's visit to Capella IV in .

With a few exceptions, all women in the Type C uniforms wore the skirt variant. One uniform seen on extras in TOS Season 1 was a woman's gold command uniform with pants. It was created for a scene in  where a pretty crewwoman was transformed into an old hag, who might not have looked appropriate in a skirt uniform. It also made an appearance in . In regards to the collars on female uniforms, blue-collared uniforms were seen in TOS and TAS on Nurse Chapel, and red-collared uniforms were seen in TAS. Female gold command uniforms were rare on both series and were never seen with colored collars. 

This uniform style was last seen in , although it was later recreated for  and .

Apocrypha 

In the IDW comic series Crew, engineering officers were depicted as wearing a Type A red uniform, with a red collar, alongside the beige uniforms as depicted in "The Cage" and "Where No Man Has Gone Before". In particular, these uniforms were depicted as only being worn in engineering, rather than elsewhere on the Enterprise, suggesting that since the engineering section of the Enterprise was never depicted during this era of TOS, such uniforms could have actually existed side-by-side with the beige Operations uniforms, thereby continuing the red division color established in Enterprise.

In the Marvel Comics series Star Trek: Early Voyages, an alternate Type A female duty uniform was depicted as a short dress with a high-necked collar, similar to the variant worn by Nurse Chapel during the late 2260s.

The alternate reality uniforms introduced in  were based on the Type C design, though the timeframe of that film, and its sequels, has them in use when the previous uniform design and the Type A was being used. Star Trek: Countdown to Darkness, Issue 2 depicts the alternate reality version of this uniform was already in use by 2239, suggesting that in the alternate reality the previous uniform and Type A were never adopted at all, unless they were used briefly after 2233.

External links 
 
 
 
 
 
de:Sternenflottenuniform (2265-2270)
de:Sternenflottenuniform (2250er-2265)
Starfleet uniform 05