I looked at that too and the darker one didn't look like Custer's personal flag; maybe the artist was unsure as to which to use and decided to include both, but disguising the blue regimental so it could not be determined what it was or assumed to be the swallowtail standard of Custer.

There are ample examples of painters in history (not all)that tend to paint based upon what they know and but what they don't know from research, they look to contemporary sources. I note that the campaign hats on the troopers appaear to be later versions that would have been in use I think at the time Paxon did his painting. Custer's troopers from my limited research wore the large black (not khaki)felt campaign hat that quickly broke down on campaign. Some troopers did wear kepis but the hats in the painting look like later 1880's versions and poplularized later by the Rough Riders.

Philip Duer