Editing a user note is currently done via the user's profile page (in the More dropdown). I just tagged you as "Photon Dev" and now whenever I see your username, that will be diplayed alongside. So, now I see this in this community:

Currently, user notes are not exposed to the api (there is a codeberg issue for this iirc) and they don't offer a way to customize the colors (I don't think there is a codeberg issue for this one). You could use custom css to style user notes since they have the css class of user_flair.