The Carbon Metallic on any Acadia you saw prior to about the beginning of August was almost certainly the original dark charcoal color.
The Carbon Black/Carbon Flash is what you will find on any Enclave and Acadia's produced within the last month or so. It is almost a pure black base color with metallic added. Maybe a shade lighter than the darkest gloss black for the base color, but not by much.
From a distance and up close, people will call it black, not dark gray, charcoal, or anything else. It does have that nice metallic sparkle though, which prevents that deep wet mirror finish you can get with a high gloss black, but on the other hand is great to help disguise small nicks, scratches, swirls, etc.