Im very intrested because will disabling dimming also disable dimming of the system title bar? I remember in KDE there is a toggle to disable dimming of the window but you can leave the title bar dimmed when losing focus vice versa, you can even disable dimming.
Since i'm spoiled by KDE's settings I don't know I can help much but I can try I guess.
I just tested this twice, with different variables. Then tested it on a copy of "Try Zorin".
It worked each time... I am not sure what is causing it not to on yours...
I wonder if you are testing it in a Flatpak application that is referencing the Flatpak Zorin themes- that is the only thing I can think of that may interfere.
The same method as above should work:
.selection-mode .titlebar:backdrop:not(headerbar), .titlebar:backdrop:not(headerbar), headerbar:backdrop { background-color: #1a2022; background-image: none; }
Replace #1a2022 with the color you want.
He using another theme, he didn't give us any system information at all?
He showed the contents of the file with cat ~/.config/gtk-3.0/gtk.css...
Ow welp, is it a part of the theme or gnome?
Theme. I tested it... Plus I recall another member had the same question about a month and a half ago and we performed the same solution, successfully, then.
Ok imma try it and try to understand it, im gonna try it on my other computer which is collecting dust anyway. I will give more feedback afterwards.
I found a solution
Yes, that also would work.
The gtk.css file placed in ~/.config/gtk-3.0 gets First Priority.
Then, the gtk.css file placed in either ~/.themes or ~/.local/share/themes gets next priority.
That is partly why I prefer edits to be made to ~/.config/gtk-3.0/gtk.css while the other reason is because edits are more easily altered or undone in ~/.config/gtk-3.0/gtk.css than they are in the Main Theme. What if you do not remember the Original parameters of the Original Theme, but it is already changed and saved?
Sometimes the accents still dim tho. I need to dig deeper in the css file. I will see what makes the shadows disappear.
U could make a backup, copy the file and rename it then save it in home folder.
Absolutely.
ctrl+F, then search for everything that has the property :backdrop
Compare the backdrop items to the non-backdrop and you can recolor all :backdrop'ed properties to match the class that is not backdropped.
(Be wary that not all items that have a backdrop property should be changed. Read what you are changing. Use the back-up copy to restore mistakes).
Nothing I tried seems to change anything.
Current system state:
redacted@redacted-lap:~$ uname -a Linux redacted-lap 5.11.0-27-generic #29~20.04.1-Ubuntu SMP Wed Aug 11 15:58:17 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux redacted@redacted-lap:~$ cat /etc/issue.net Zorin OS 16 redacted@redacted-lap:~$ gsettings get org.gnome.desktop.interface gtk-theme 'ZorinBlue-Dark' redacted@redacted-lap:~$ cat /home/redacted/.config/gtk-3.0/gtk.css .background:backdrop { color: #bde6fb; background-color: #1e2529; } redacted@redacted-lap:~$ cat /usr/share/themes/ZorinBlue-Dark/gtk-3.0/gtk.css | grep .background:backdrop .background:backdrop { color: #6f828a; background-color: #1a2022; text-shadow: none; -gtk-icon-shadow: none; } /* I manually inserted the following .background:backdrop */ .background:backdrop { color: #bde6fb; background-color: #1e2529; } popover.background:backdrop { background-color: #14191a; box-shadow: 0 1px 2px 1px rgba(0, 0, 0, 0.4); border-color: rgba(40, 48, 51, 0.75); } redacted@redacted-lap:~$
The system was freshly installed about a week ago, and wasn't customised at all (except for the changed theme to dark in Zorin Appearance app). Is there any other information I can provide?
Thank you all!
Can you post screenshots showing the dimming effect?
That is the same as I see on mine due to the backdrop property in the theme. I do not see anything there to suggest an outside Dimming Effect...
I am honestly at a loss.
The suggestions above should work and have worked on each instance I tested.
Ok... can you try a third party theme (It doesn't matter if you like it or hate it... just something that can give us a frame of reference to compare against) and see if you observe the same dimming effect?
You can snag one from Pling.com
The next test will be to use the ~/.config/gtk-3.0/gtk.css to make some obvious change that is easy to observe, like
button*
{background-image: linear-gradient(to bottom, pink, orange);
}
To see if that causes a direct and easy to see change. If so, then we know that the file is being seen and used by the engine.
I've tried several themes, and while most of them do some sort of the dim effect, I've found several that don't. One example is Qogir-win-dark. I honestly don't care much about the theme as long as it stays out of the way... I'm ok with staying with this one.
I've tried gradient from the post above, and i don't see any change. Weird...
Very weird.
The most I can offer is the suggestion made above in this post...
Copy the Zorin Theme you prefer to ~/.themes
Then modify the theme gtk.css file.
Correction, the button css did apply, but only to some buttons (not all programs), so I didn't spot it right away.
Some windows where it did apply:
And now you know how to prank another Linux user. 
Well, have established that your gtk.css is being read.
What it may be is you and I are looking at different changes (different things have our attention.) We may not have enough classes listed in your gtk.css
We could try isolating each class; or take a riskier move using the * option
For example
window.background:backdrop* { color: #bde6fb; background-color: #1e2529; }
