The system icons integrate nicely with the theme, but custom icons don't.
The 2 on the left stay white, while the others change color based on the theme
Is there a way to maybe choose an icon from the default ones for every icon in the tray so they integrate nicely?
That has also really annoyed me. The only way I have worked round it is to use a semi-transparent bar that allows them to pass through.
I think it's possible to change the icons, so I was thinking of making icons all in the same color. They won't match the system icons, but at least match each other.
But having them change along with the system icons would be better.
I think that it depends from what software they come. Are these Indicators from an Extension or a Flatpak/Snap Program?
I have one from an extension, and that once changes color along with the system icons.
The ones that come from programs have a fixed image.
The icons in question are the Symbolic icons located in the "symbolic" directory in each Icon Sets folder in /usr/share/icons/... or user applied ~/.icons/...
Symbolic icons tend to be monochromatic in light or dark and very basic with details.
Many applications will call on the symbolic icons for the tray or other locations that display icons in a very small or harder to see format.
There are a few that instead supply their own icon in a folder contained within that applications own directories - but not many apps do this.
And these Programs: Are these Flatpaks/Snap's or .deb's? Because Flatpaks/Snap's can be a bit tricky because there are running in Containers. And so there have only limited Permissions.
For flatpack apps the tray icons are located here:
/var/lib/flatpak/exports/share/icons/hicolor/scalable/apps/
Changing the images here will change the tray icon.
Any idea how to do this for apps installed with apt?
Apps installed with APT should show in /usr/share/icons/hicolor/apps but you may need to explore hicolor a bit. Often, an icon specifically for use in the panel (taskbar) will be labeled with its name_tray
There is some annoying variance... Some apps will instead place their icon in the more general location of /usr/share/pixmaps which is an older practice that lingers.
It can help to use a file searching utility (I use the built in search in Nemo FM) if having trouble locating a tray icon.
Actually you can adjust the color (white and black) of the system tray. Find Zorin Appindicators and tweak away.
Cool!
Desaturating the icons makes them fit way better!
Not all flatpak tray icons are in this location: /var/lib/flatpak/exports/share/icons/hicolor/scalable/apps/
Any other locations tray icons could be in?
For Flatpak, I am not sure.
I would think it would definitely be contained and relegated to the path you show since Flatpak is containerized, it should not place elements elsewhere in Root.
Nope, but if you figured out, please let me know 
