Created attachment 7000 Screenshot demonstrating the problem I an not 100% sure that I am reporting the bug against the right component, since the power manager seems to have two panel applets: One can be added from the power-manager settings and one from the panel applet list (it is, however, not an extra applet, at least in its information dialogue it is called xfce4-power-manager). The applet which can be added from the applets list has a font colour which is unreadable on dark panels, see attached screenshot. The issue has been discussed here: https://forum.manjaro.org/t/xfce4-power-manager-1-6-badly-visible-on-panel/11537
This is a theme issue and needs to be fixed by the theme designer. As a work around, try adding the following to ~/.config/gtk-3.0/gtk.css: #xfce4-power-manager-plugin { color: #ededed; } ...and restarting the panel (make sure you include the # sign, it is not a comment but rather a widget identifier).
Thanks, forwarded this information to the theme maintainer!