- Compatible XF 1.x versions
It took me the better part of a day, but FINALLY I stumbled upon the solution. I first had to invert the original and then colorize the image.
(The preview shows it against a dark background, but the background is transparent on the file. The preview doesn't show all the icons, the preview is much too long and would be compressed by xenforo.)
- Check the path and the file name that your theme uses by going to: Style Properies -> Rich Text Editor -> Editor Toolbar Button - Background Image Property.
- If the value is empty, find which color you want, rename it to icons.png, then upload it to /styles/default/xenforo/editor/
- If there is a value in Background Image Property, then find which color you want, rename it to icons.png (or whatever the theme named it), then upload it to /styles/YourStyleName/xenforo/editor/
- Go into your forum, and check your editor. If you don't see a change, hit F5 or Ctrl+F5.