Starfleet uniform (2390s)

The Starfleet 2399 uniform (SF 2399) was a type of clothing, a color-coded uniforms worn by personnel of Federation Starfleet at the end of the 24th century. The overall design harkened back to the colorful aesthetics of the previous three decades. (STO - "Season 18: Awakening" mission: "Welcome to Earth Spacedock")

History
SF 2399 was adopted in the 2390s, and in use by 2399. (PIC episode: "Remembrance")

Of previous styles, SF 2399 most closely resembled a uniform style worn around 2387. (ST - Countdown comic: "Number One")

These two styles were later adapted to the Sierra uniform of the early 2400s. (STO - "Klingon War" mission: "Welcome to Earth Spacedock")

In 2410, the SF 2399 uniform was made available again to wear for officers of Starfleet. (STO website: Claim the Uniform of Star Trek: Picard!)

Appearance
The Starfleet 2399 uniform was a two-piece attire, rather than a jumpsuit. The long-sleeved top, undershirt, trousers and boots were a matching black. The shoulder part of the top was colored specific to the department: red for command, yellow for operations (tactical and engineering), and blue for science and medical. In the 25th century, tactical had switched to red. (STO - "Klingon War" mission: "Welcome to Earth Spacedock", STO website: Claim the Uniform of Star Trek: Picard!)

In the 2390s, the uniform was worn with the SF 2399 combadge - a golden, hollow Starfleet arrowhead atop two dark grey, vertical bars. (PIC episode: "Remembrance") This combadge was reminiscent of a design in use in different alternate timelines and potential futures. (TNG episode: "All Good Things", VOY episodes: "Timeless", "Endgame", DS9 episode: "The Visitor")

While both combadge designs were available for Starfleet officers from 2410 onwards, only the SF 2399, the Lifetime combadge and a plain arrowhead could be worn with the Starfleet 2399 uniform.

The combadge colors could be changed within a limited palette of gold, silver, bronze and dark grey. (STO - "Season 18: Awakening" mission: "Welcome to Earth Spacedock", tailor menu)

The combadge was worn on the left breast, with its top crossing the dividing line between department color and the black main body of the attire. Round, golden rank insignia sat just above that dividing line over the right bosom. In the center of the chest, a small trapezoid of division color angled downward. Admiral rank insignia also consisted of round pins but these sat inside a trapezoid. (STO website: Claim the Uniform of Star Trek: Picard!)

In contrast, the 2387 uniform had the trapezoid angle up, and its rank insignia were golden squares instead of round pins. (ST - Countdown comic: "Number One")