I’ve also never heard of a carry-in (New York State, mostly, though I’ve been elsewhere); but I have run into two contradictory definitions for potluck, though the first is IME much more common:
Everybody, or nearly everybody, brings a dish to pass, which will be set out so everyone can choose from the selection.
The host provides all the food, but the invitation is spur of the moment, so the guest will be provided a share of whatever the family would have eaten at that meal anyway: the guest takes their chances of whatever’s “in the pot”, which might be anything from prime steak to stale cereal.
– there are also subset versions of definition 1: the host may or may not assign either specific dishes or categories of dishes (which takes some of the “luck” out of it, if they do); and the host may or may not specify that they’re providing some portion(s) of the meal, usually the main course if so.
I have never seen it green in my life, just clear, but usually in an opaque bottle. I’m curious where you are, because I would walk past that a dozen times in scanning mode as brain just checked off “definitely not rubbing alcohol” and moved on without reading.