Starfleet Uniforms have undergone several changes since the organisation was founded in 2161. Various different amendments have been made due to changes in requirements of serving officers, new materials becoming available, political concerns about the appearance of the organisation and cultural sensitivities to the many members of the Federation.
Current Uniforms - 2395
The current Starfleet uniform was brought into service in 2395. In a return to the stylings of the 2350s and 60s, the grey utilitarian fatigues were phased out and replaced with the bright service colours making up the main shirt colour.
Uniform codes are administered on a ship by ship basis and many captains do not follow the regulations to the letter. It is common for some commanders to allow their crew to eschew duty uniforms and stick to fatigues; some positions, like Ship's Counsellor or Chief Medical Officer, are permitted greater latitude and allowed to wear non-standard clothing while on duty - and indeed Captains and Admirals themselves can wear customized uniforms of varying design.
There is also a tradition of allowing officers to wear religious or cultural items while on duty so head-gear and jewellery may be added if there is a traditional reason behind it and it does not impede an officers duty.
These are not, however, inalienable rights and they are at the captain's prerogative. Some TacFleet commanders in particular insist on strict uniform discipline.
Duty Uniforms - Officers
This is the standard uniform to be worn aboard ship while in service by officers. The bright colouration is intended to mark them out from a distance.
This is composed of black boots, trousers and undershirt. Over this a coloured jacket is worn, fastened slightly off-center and with colouration depending on branch of service - Red for Command, Blue for Science/Medical and Gold for Tactical/Engineering. A similarly coloured belt holds the trousers in place.
Along the shoulders is a silver stripe, which names the ship/station the officer is posted at as well as their surname. Above the bar is their rank insignia - below is their commbadge in the shape of the Starfleet insignia. There is a silver tripe on each cuff.
Note that Admirals have their own, white coloured variation of this jacket though they can also choose to remain in their service colour. (Usually Command Red, but some senior postings see an Admiral rank in the other branches.) There is also a "diplomatic uniform" for members of the Diplomatic Corp serving on ship.
Duty Uniforms - Enlisted
This is the standard uniform to be worn aboard ship while in service by enlisted men and women. The darker coloured outfit is intended to be more practical for their often more manual jobs.
This is composed of black boots and trousers, along with a coloured undershirt - Red for Command, Blue for Science/Medical and Gold for Tactical/Engineering. Over this is placed a grey jacket, fastened to the center, and a grey belt for holding the trousers in place.
Along the shoulders is a thin black stripe. Above this stripe is the name of the ship/station the crewman is posted to followed by their rank insignia. Below is their commbadge in the shape of the Starfleet insignia. There is a silver tripe on each cuff.
The fatigue uniform design was in service during the 2350s and 60s before being rotated out in 2373. It was returned to service at the request of Exploration Command, who wished to be rid of the previous "grey" uniform so associated with the Dominion War.
This is composed of black boots and trousers, along with a purple undershirt. Rank insignia is attached to the right hand of the collar of the undershirt.
Over the shirt is worn a jacket, black with a coloured shoulder section - Red for Command, Blue for Science/Medical and Gold for Tactical/Engineering. A Starfleet insignia is worn on the left breast.
This uniform is much looser fitting than the others, designed for use by all ranks and for field postings.
Two different dress uniforms standard are used by Starfleet: Mess Dress and Full Dress.
Full Dress is reserved for major events such as visits by heads of states, inspections by flag officers, funerals, memorial services and similar ceremonial events. All officers wear white boots, trousers and a white jacket which fasten off-center and with silver cuff stripe. Enlisted men wear a branch-coloured undershirt, officers wear a silver one and flag officers gold. Officers and flag officers also have belts, shoulder stripe and epaulets coloured as their undershirts. A Starfleet insignia is worn on the left breast.
Mess Dress is the form used for official balls, dinners, evening dances and similar social receptions. This resembles a tuxedo or similar outfit. Officers wear black boots, dark grey trousers with gold crease-lines and black undershirt. A black jacket with gold piping is worn over this, fastened centrally - officers have silver cuffs and central section, flag officers have gold. A Starfleet insignia is worn on the left breast.
The enlisted Mess Dress is a similar design but in white rather than black and grey. The Enlisted version has a silver undershirt, silver central section and gold cuffs.
Notable variations on dress uniform can be found - some unique to specific races, ships, service branches etc. Perhaps the most common example is that female officers can also elect to wear an appropriately coloured ankle-length skirt in place of the trousers.
Enlisted men and women wear a rank insignia that is a silver bordered hexagol. The higher ranked they are, the more detailed the contents are - from blank to smaller hexagons to Starfleet insignia.
Officer ranks are shown with rectangles, either solid silver or black with a silver border. The black bar is always shown facing away from the neck.
Silver bars inside an additional silver border is the mark of flag officer rank.