the white precedes trujillo. horacio vasquez was also fond of white suits:
here he is during military parade:
with american mission:
and with more american politicians:
i'm guessing the white had a lot to do with do-nothing appearance. a worker or low class citizen would have more practical clothing. white might have been a part of status symbol, so to speak.
as far as diplomatic and political dress code goes, i have read a booklet for polish diplomats and it's very specific when practical details are concerned. from dressing yourself to dressing the table for parties. some countries have specific sets of rules for particular countries/cultures to make sure the staff is behaving accordingly.
the same goes for politics and political/government acts. even the members of the public are forced to keep certain decorum (dress code in government offices is a good example here). when i toured palacio nacional with one of the staff there was also a lot of do's and don'ts during the visit.