Once a comment is saved, you can edit it either from the Comments window, or from the source itself. Editing tags is the same as editing comments.
You can edit content, change status assigned to comments and tags, and delete comments and tags. You can also renumber tag and comments IDs, if necessary (see Manage Comment and Tag IDs).
You can use the
Thickness and
Color controls on the
Review tab 
Markup panel to modify the way tags will be drawn in the
Scene View. These changes do not affect already drawn tags.