I believe that I have seen a few of the "Shuttles" around
SFO recently. I suppose that they don't see a need, considering their current financial situation, to bother restoring those a/c to the standard
UA livery. In addition to the Shuttle livery you mention, there are also some old Shuttle a/c that have "Shuttle by United" with Shuttle in a cursive font. If I'm not mistaken, those a/c are white (?).