those are the bootswatch-themes applied over the theme.
but since bootswatch-themes mainly overwrite bootstrap-variables it gets overwritten again by any theme other than vanilla.

I don't think this order is intended since I'd apply the bootswatch-variables after the theme-styles therefor it's in the admins control. But maybe the devs thought that the theme-developers shouldn't overwrite skin-able variables...

Also (currently?) not working: @julian @baris @psychobunny

hide "revert skin" from themes-list when no skin is applied theme-change (to vanilla) after selecting skin doesn't persist skin no indicator which skin is selected as of runtime less-compilation the alert to restart NodeBB after skin-selection isn't necessary, is it?