I do not want to install icons in dom0. But I do want to change the icons seen in the screenshot (especially the devices- and qubes-icon). (Or at least make those icons grayscale, as the other icons are also in grayscale.)
Where do I find them? How are they named?
I have read this, but it does not help: https://forum.qubes-os.org/t/improving-white-background-systray-icons-for-dark-themes/
It is necessary to understand that some of those icons might not be actual png or svg files but rather dynamically generated. Examples are WiFi signal strength icon and Tor connection status icon. There are easy workarounds to make them grayscale. Just change the label color of the VM which the tray icon app belongs to to gray. But since that trick won’t have any effect on Qubes Domain and Qubes Devices systray icons, here are their actual location for Qubes Domains:
find /usr/share/icons/hicolor/ -name "qui-domains*"
And systray icons for updated (which is usually black by itself):
find /usr/share/icons/hicolor/ -name "software-update*"
etc.
If you know python, you could check qubes-desktop-linux-manager repository and inspect how and which icons are loaded. Changing the icons is possible in many cases via changing the icon files or the code. But that would be invasive plastic surgery and I advise against that.