Tags in lower left don't seem to exist in the library

ssmithtr

I have 'Display All Tags in This Library' turned on. I am in the primary library folder, not a collection. There are tags with assigned colors that are grayed out but still present in the lower left pane. I cannot find any entry within that Library that is using those tags. The 'Trash' folder is empty. Why do they still exist in the list if nothing in that library uses them? Is there any possibility that they're being pulled from another library's tags?
Is there a way to find out where they are coming from so I can decide if I should delete them or not?
Thanks

adamsmith

colored tags don't disappear unless you unassign the color. If they're greyed out, they're not assigned to any item.

ssmithtr

Thank you @adamsmith. I didn't realize they would persist even if they weren't used anywhere in the library, but that does make sense if they've been prioritized like that. I appreciate the clarification.