In the time of Night Watch, a porter at the Assassins' Guild. Mr Maroon was inadvertently helpful to the young Vetinari on a number of occasions (for instance, active assignments were pigeon-holed in alphabetical order, right underneath the great big word "ACTIVE", so that from the other end of the hall, Vetinari could see there was one under "B" and make the deduction that the Hon John Bleedwell, Esq., was out on a mission). Mr Maroon quite liked Vetinari, rating him as a quiet and studious young man, with a polite interest in the welfare of the Maroon family, which many of the other young gentlemen would not even think to have for a social inferior. Vetinari has also taken care to be "appropriately generous" when the occasion calls for it, and has made a useful ally, giving him an edge over other assassins who wouldn't even think to ask after the welfare of a mere servant's wife and child. Like the Stipplers, the Maroons are "hereditary porters" to the Guild, in that their fathers and grandfathers were Assassins' Guild employees, and their sons and grandsons in all probability will be.
There also used to be a Sergeant Maroon in the Watch. In Men at Arms, it is revealed that Sam Vimes is paying his widow a pension, of sorts. it is unclear whether the Maroons who are hereditary porters at the Assassins' Guild are related to the Watchman of the same name.
A coal-merchants' on Wixon's Alley are also called Maroon and Sons. Whether they are related is not yet made clear.