So it looks like this is not possible with theme components as there doesn’t seem to be any templates/components for this 
Appears this Ruby module is injecting inline styles: discourse/lib/category_badge.rb at 888e68a1637ca784a7bf51a6bbb524dcf7413b13 · discourse/discourse · GitHub
Was this meant to be a temporary measure? If not, do you think it would be possible to allow us to specify custom styles please @sam?
It code be tied to the existing none option, where we could have two fields in the admin settings panel where we could paste our styles for each (if no styles are pasted it just acts like the none option acts now):
<span class="badge-category-bg" style="background-color: #25AAE2;"></span>
and
<span style="color: #FFFFFF;" data-drop-close="true" class="badge-category clear-badge restricted" title="A category exclusive to members with trust level 3 and higher."><svg class="fa d-icon d-icon-lock svg-icon svg-string" xmlns="http://www.w3.org/2000/svg"><use xlink:href="#lock"></use></svg><span class="category-name">Lounge</span></span>
From this snippet:
We would just need access to the background colour and text colour variables from the usual category-edit page.
Or is there any other way we can edit this Sam? I just want to remove the background colour and give it a border that is the same colour as the text (as specific in the usual category-edit page).
Any help would be greatly appreciated.
Edit: appears that it’s not that Ruby file after all (I edited it on my dev install but nothing changed).. further digging and it seems like it’s this one: discourse/app/assets/javascripts/discourse/helpers/category-link.js.es6 at b25d9e96c1414bf78b44221da4d385675843991e · discourse/discourse · GitHub is there any way to create a plugin to modify it?