Add CSS rules for basic colored labels (#23774) (#23777)

Add CSS rules for basic colored labels (#23774) (#23777)

Backport #23774 by @silverwind

Before:

<img width="164" alt="Screenshot 2023-03-28 at 23 35 46"
src="https://user-images.githubusercontent.com/115237/228372437-663111b9-7285-4fa2-9125-fb5e1cad21d7.png">

After:
<img width="166" alt="Screenshot 2023-03-28 at 23 35 54"
src="https://user-images.githubusercontent.com/115237/228372441-49430517-6b2d-4389-b11c-c30a724f6de7.png">

Also I removed the `!important` on the primary label as it's very likely
unnecessary with the amount of specificity the selector already has.

Co-authored-by: silverwind <me@silverwind.io>