1) Pertaining to hipster subculture. Derived from previous uses of "collar" to describe class:
blue-collar, white-collar,
green-collar. Conotes the, perhaps, more mature subsection thereof.
2) Used to describe a class of professionals (after the fashion of white-collar, and
blue-collar) who work in fields associated with information, creativity, social-media, etc.
3) Liberal arts majors who manage to get a job where they only wear ties if they feel like it, and with the top button undone.
Hipster 1, "Winston just got a job at the Huffpo as a social-
media coordinator."
Hipster
2, "Totally, kewl, joining that plaid-collar workforce."
"Dude, I forgot my rooibos
tea, at the new lunch-time yoga studio...man, I'm totally a plaid-collar worker."