"Moth-like, the people buzzed about, walking, driving, directing, each to their own light."
the last em dash (-) is not really appropriate, as that piece of data is very much a continuation of the last few pieces of data (i.e., the metaphor of their movement). The comma here actually is not needed grammatically, I think, but I added it for the natural pause (that you marked with the em dash).
The colon also feels out of place, though not completely off. It cannot be a semicolon, as the second clause is not an independent one... And a comma would not suffice here, not would a full stop.
The first comma is of course to accomma(heeeey)date the irregular sentence structure.
It's a tough one. I'm open to suggestions.
EDIT: Add Punctuation Guide (informal)