The Jumpsuit is the main piece of Clothing that you will wear in the space station and indeed, you Spawn wearing one of these, as well as a pair of Shoes and any other Peripherals your Proffession begins the Round with. It is equipped in the central i_clothing slot. Having a jumpsuit on has several effects.
Firstly, it stops you displaying all that unsightly flesh! It also lets you equip an ID card and Radio Signaller, and provides you with two pockets, in which you can store one small object each, such as a pen.
There are several designations of the standard Jumpsuit:
Blue: Found in supply lockers around the station, the fluff states it is for recreational purposes. (Used by captain and head of personnel on the /tg/station)
Grey: Used by the Assistant Profession. This colour is found in "grey" Lockers around the station.
Red: Used by Security Staff, this colour can be found in "red" lockers in the Security Station.
Pink: These are the female version of the standard Blue Jumpsuits, and are found in "unisex" and "pink" lockers.
Dark Green: Used by the Captain only.
There may be more, please add to this.