This would be a good way to subtly “remind” the user which account they’re currently using/logged in as.
This would basically involve either (a) moving the “primary color” widget from the “appearance” section to the “account detail” page; or (b) making the “primary color” widget into a sub-section of its own, and where each account is listed.
Oh my god this would actually be amazing! Needs some thinking about though. Like if you want them all to be the same colour but not the default one, having to go in and set it for each of your accounts would be annoying. So maybe the colour setting stays where it is but then each account has kind of an optional “override”? This is just off the top of my head I’m sure someone better at UX than me has a better idea.