Category badge can get lost in the background

This is pretty minor, but given that the issue is present here on Meta when using the dark theme, I thought it might be worth bringing up. The problem occurs when using the same (or very similar) background color on both the overall forum and a category badge. The badge gets lost in the overall background. See the dev category in the photo below for illustration:

I suppose the simplest solution is to change the badge color, but if that's not desirable, another fairly subtle way is to add a thin border. Maybe something like this:

Applied via:
.badge-category-bg {
   border: solid .5px #3f3f3f;

Just something to chew on.

Perhaps a different box shadow would work? Currently it looks like we use a black box shadow with 25% opacity. On an already black background that’s not really seen. Could a white box shadow make it stand out more? cc @awesomerobot