Yellow uniforms are worn by senior executives and department heads, including Kirk. Blue uniforms are for science officers, including Bones and Spock, while red uniforms are for officers involved in operating and manning the ship.
As for Chekov, his character was originally supposed to be a “Kirk-in-training” on the command track, so he wore command gold — er, green — whatever. p>
I recently noticed that Lieutenant Uhura, the Enterprise communications officer, played by the stunning Nichelle Nichols, wears a red uniform. This may not come as a surprise at first. In the original series, many people wear red uniforms.
Division or section assignments are indicated by a colored circle behind the delta, rather than the uniform color itself: red represents engineering, light green represents medicine, orange represents science, white represents command, pale gold represents operations and gray for security reasons.
Representation. Uhura from the United States of Africa speaks Swahili and was born on January 19, 2233. James Blish’s non-canon novels identify them as Bantu, as does Gene Roddenberry’s novelization of Star Trek: The Motion Picture.
Troi holds the rank of Lieutenant Commander when she first joins the Enterprise-D; The spikes are clearly visible on her collar in Season 1 Episode 1, “Encounter at Farpoint”. After that, however, she no longer wears them on her civilian clothes, suggesting that she prefers a more informal relationship with her fellow officers…
Kathryn Janeway is another good example – she wears red because of her role as Captain, but most of her experience is that of a physicist and scientist. In fact, prior to becoming XO of the USS Billings, she was the ship’s science officer.
Determining the wearer’s career is the primary function of a Starfleet uniform. In TOS (The Original Series), gold was reserved for command, red was for engineering and security, while science and medical officers stayed blue.
In The Making of Star Trek: The Motion Picture, Roddenberry explained that the uniforms were redesigned because the bright original colors would distract viewers on the big screen. However, these changes proved unpopular and were redesigned again for the later films.
So if red is engineering, it makes sense for TOS Uhura to wear red because she’s effectively a communications gear engineer.
One of the unique attributes of Worf’s character is the fact that he wears a sash or baldric to honor his Klingon heritage. First he wore a golden sash, a replica of the baldrics worn by Kor and Kang in TOS.
The term comes from the original television series Star Trek (NBC, 1966-69), in which the red-robed security guards often die during episodes. Redshirt deaths are often used to dramatize the potential danger faced by the main characters.
The Captain’s uniform was designed by Robert Blackman to differentiate Captain Picard from the rest of his crew at the suggestion of actor Patrick Stewart.  The creation of the jacket was prompted by Stewart, who complained about how uncomfortable standard service uniforms were.
The couple is explicitly separated in the film and never gets back together.
Spock and Uhura have a canonical love affair in the Star Trek Alternate Original Series movies . Originally envisioned as student and teacher, later scenes establish that Spock and Uhura are also romantically involved (Uhura comforts Spock with a hug; in a later scene, the two share a kiss).
Both the Star Trek: The Original Series episode “Amok Time” and the film Star Trek III: The Search for Spock state that Pon Farr is specific to Vulcan males. This is therefore in conflict with ENT: “Bounty”, in which pon farr is attributed to both sexes.