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 white-icons|98x29 to color-icons|97x28

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.

[details="network-wired-symbolic.svg example"] 

<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">.ColorScheme-Text { color:#dedede; } .ColorScheme-Highlight { color:#4285f4; }</style>
 &lt;/defs&gt;
 &lt;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"/&gt;
&lt;/svg&gt;
[/details]

You can change all the files in the folder with a shell script.

#!/bin/bash
for file in /usr/share/icons/&lt;theme&gt;/22/panel*.svg; do
   sed -i '2i &lt;rect fill="#color" width="xx" height="xx"/&gt;' $file
done

You are going to have to remove background from images that are drawn on top of another image, e.g. the vpn lock icon.