Did you try changing the preferences in about:addons? There you can customize the colors so that they match your theme.

So please get your facts straight before criticizing. Actually, it was me who designed and implemented the WebExtension API that Firefox provides to add-ons so that they can change the text color of the badge! See https://bugzil.la/1424620

On the other hand, I agree that it would be great to automatically pick the colors depending on whether the theme is light or dark. But, as said in issue #15, the problem is that I can't properly do it with current APIs. So in https://bugzil.la/1484840 I proposed a new API, but I don't have time to implement it and convince Mozilla to accept it.

Edit: OK, turns out the problem is about the popup, not the counter icon. That's different than the existing bug report from 2018, and seems fixable. I was not aware of it, thanks for the report! Sorry I was too quick to jump to conclusions.

This problem wasn't actually my fault, since I was just relying on the browser to provide the correct text and background colors. But I have addressed it in version 3.3.