What exactly are the objective criteria for "the feel of AARoads"?
When I designed the existing forum theme, the design objective was to create a user interface that evoked the subject matter of the forum (roads, primarily in the US) by using the existing design language of the U.S. road system (that is, the MUTCD) as much as possible. So the "quote" and "edit post" buttons are blue squares, evoking blue square services signage, the "NEW!" icon that shows up on topics with new posts is a modification of the "NEW" banner in the MUTCD, and so on. The grey bar at the top of each page (and above the Quick Reply box) has a pavement-like texture. And of course, the primary color is green, because that's the color of guide signage.
Since the subject matter of the forums hasn't changed, I see no reason why the design language of the forum should either. So a dark version of the forum theme would ideally stick to the same principles, but just use darker greens and greys where appropriate.