As a side since it's come up a few times.. Same model, different mission/role. Antarctic mission (20 return trips) are done for the season until January when they start pulling back out again.
Here we see 3 different 'tails'. McChord/green tend to do bulk logistics. Charleston/yellow are occasional (presumed DoD or specialist crew) and Stewart/black seem to do a personal/staff drop/pickup at each end of season



