Reply To: Change user color
it is not good practise to amend bbpress (or any plugin) files.
The code should go in the custom css area of your there if it has one, or via a plugin such as https://en-gb.wordpress.org/plugins/simple-custom-css/
for the threads are, the simplest would be to use my style pack plugin
and change the roles in
dashboard>settings>bbp style pack>forum roles
for your specific area, we would need the code you added in your functions file, but that should be able to then use the plugin settings above
