Starfleet uniform (late 2270s-2350s) Officers

The Starfleet uniform of the late 2270s through the 2350s represented a radical change from older uniform designs. Around this period, Starfleet abandoned the practice of using individual insignia for each mission or starship. From this point on, all Starfleet personnel wore the "arrowhead" insignia previously used by the crew of the USS Enterprise and the USS Kelvin. The uniforms of this period bore the new Starfleet insignia on a brass-colored pin worn on the breast; officers wore the insignia with a round-ended rectangular shield backing it. New rank insignia, with individual symbols for each rank, were also introduced, and were worn on the clasp and left wrist of the tunics. This uniform style was phased out in the 2350s after undergoing several minor changes. It was Starfleet's longest tenured uniform design to date, having been used with variations for over almost 80 years.

 Officer uniform
Late 2270s to 2290s
By 2278, the officer uniform sported black trousers and a double-breasted red jacket worn over a turtlenecked undershirt. The undershirt, along with stripes on the pants, shoulder, and left sleeve had distinctive division colors. The jacket closed by a clasp at the right shoulder and a sealing mechanism that ran along the black stripe. This allowed the wearer to have a more relaxed appearance and likely allowed more circulation of air. An optional skirt was available for female officers. (Star Trek II: The Wrath of Khan, Star Trek III: The Search for Spock, Star Trek IV: The Voyage Home, Star Trek V: The Final Frontier, Star Trek VI: The Undiscovered Country, TNG: "Cause and Effect")

 Flag officer uniform
Flag officers with service ribbons
Admirals wearing service ribbons
Flag officer uniforms were the same as the officers uniform, except that the pants stripe and tunic were trimmed in gold.
In the 2280s, flag officers who were part of the Federation Council wore stylized pins centered on the breast of their jacket. (Star Trek IV: The Voyage Home)
In the 2290s, flag officers wore service ribbons on the left breast of the jacket, below the Starfleet insignia. These ribbons varied in color and position, and likely indicated different commendations and awards received by the officers for their service in Starfleet. (Star Trek II: The Wrath of Khan, Star Trek III: The Search for Spock, Star Trek V: The Final Frontier, Star Trek VI: The Undiscovered Country; Star Trek Generations

Mr. Scott's Guide to the Enterprise