If you are having issues with your systray icons having white background this might improve the icons, if you are using SVG icons.
It will make the icons go from to
First you need to find the folder with the systray icons, icons can be installed in ~/.icons or /usr/share/icons
A good place to start would be /usr/share/icons/<theme>/22/panel, but it might not be the same for all themes.
SVG files are text files, and you can easily add a background, which removes the white background.
Add this line after the svg tag <rect fill="#ffffff" width="22" height="22"/>
Make the color match your xfce panel background color, and the size needs to be the same as the pixel size of the folder you are in.
<svg width="22" height="22" version="1.1" xmlns="http://www.w3.org/2000/svg">
<rect fill="#ffffff" width="22" height="22"/>
<defs>
<style id="current-color-scheme" type="text/css">.ColorScheme-Text { color:#dedede; } .ColorScheme-Highlight { color:#4285f4; }</style>
</defs>
<path d="m4 5c-0.554 0-1 0.446-1 1v4c0 0.554 0.446 1 1 1h1v6h1v-3h5v2h-3v1h7v-1h-3v-2h6c0.554 0 1-0.446 1-1v-7c0-0.554-0.446-1-1-1h-12zm0 1h3v1h-3zm4 0h10v7h-12v-2h1c0.554 0 1-0.446 1-1zm-4 2h1v1h1v-1h1v2h-3z" class="ColorScheme-Text" fill="currentColor"/>
</svg>
You can change all the files in the folder with a shell script.
#!/bin/bash
for file in /usr/share/icons/<theme>/22/panel*.svg; do
sed -i '2i <rect fill="#color" width="xx" height="xx"/>' $file
done
Optional In the global settings, set the tint saturation to 50%.