Purpose: to create an atmosphere of "uniformity", or, compliance, if you will. E.g. Scrubs: pink = nurses. navy blue = techs (nurses aides, etc), teal green (OMG, surgeons), purple (I, don't know...maybe housekeeping/custodians), let's see, then there is the cafeteria staff.......A monkey suit is a uinform that one wears to work every day. The military does it, sanitary engineers do it...I could go on. Benefit: Does save money on duds.
A suit used to convert one's outward appearance to the guise of a monkey. This term was most prevalent in the inspirational movie "Going Bananas" in which Bonzo, a midget woman from Los Angeles encounters an identity crisis, eventually winning the US Open all while fooling America into thinking she was a 7 year old monkey tennis champion.
Jim: You, sir, are wearing a monkey suit!
Marbles: (Tosses monkey excrement at Jim)