Styling tray icon color with gtk.css

[Ayman29996266]

Hey, I'm not sure if I can call it a bug, I just found out I can't style the tray icon color with my css file like I usually do with other status notifiers like telegram, pipewire or blueman..
I usually assign them a symbolic (monochrome) icon and let a script style them every now and then. But this icon just doesn't seem to change color at all.. All other properties are fine as far as I tested.

The icon should change it's color to match the other icons as in this screenshot:

Thunderbird 128.4.0-1 ( repository package installed with pacman )
SysTray-X 0.9.10

My device:
HP Zbook / 64 bit architecture.

I use:
Arch Linux ( 6.11.6-arch1-1 )
X11
GTK 3
XFCE4
XFCE4-panel.
The css file I use for styling is in: ~/.config/gtk.3-0/gtk.css
example css code to style the icons color:

#sn-button image {
  color: red;
}

NOTE: To see the changes you make in the css file you need to refresh the xfce panel with this command: xfce4-panel -r

Thank You !!

[Ximi1970]

I am using Qt for the icon and have no css styling build in.