Maybe it is the costumer's favorite color, maybe the people on the Island are huge fans of Gogol Bordello, but I've noticed a lot of the characters wearing purple this year.
A look into the history of purple will show a list of minority or, fringe and status related groups and ideas. The Nazi's used purple badges during the Holocaust to identify people of an un-orthodox religious standing.
In higher education purple is worn on the robes of the Dean and staff with tenure, as well as on the robes of those studying theology.
Purple is associated with the sun in some asian cultures, example: wikipedia has it listed as the color the Thai calender uses for Saturday on it's solor calender.
purple has long been a part of royal life in almost every ancient culture.
Amethyst is the color of the CROWN chakra.
Egyptians who wore purple were showing their faith and integrity.
In middle eastern culture a purple glow around the sun or moon during an eclipse is believed to be a forewarning of death and destruction.
And of course, the purple heart, a medal given to someone who has been wounded in military service.
Lastly, I tattoo for a living and most people want purple in their tattoo's because it's pretty, and this may be the reason so many people wear it this season. But Alpert and Mock-Locke? maybe it's not a coincidence.