@marmarek In the dom0 terminal I executed the following command:
sudo qubes-dom0-update --enablerepo=qubes-dom0-current-testing
After updating, I rebooted my machine and the Network Manager tray icons are still white. The tray icons for other apps in running VMs are also white.
Thoughts?
( I installed Qubes with the 4.1.0-rc2 iso image and updated the DM to KDE following advice from @Sven in KDE - changing the way you use Qubes - #8 by Sven)