If the tag is in your existing tag cloud, the value typed and all surrounding tags would appear ‘Papaya’ in color.
conversely
Typing to add a new tag value, the entry will appear ‘Sky Blue’ once a unique value is observed. And, it would be real skookum if the tag algo had knowledge from tag aliases IE; macOS, MacOS, macos, etc.
Almost zero forethought has been attributed to this post.
In the images above, you can see I’ve colored the three different “macOS” that appear in different databases.
If I open any document and add the macOS tag from “info” in the Inspectors sidebar or via the bottom “Tags” bar, only one version of “macOS” appears in the drill down.
Tags are not global so you will only see the tag from the database of that document. You’re not going to pick a tag from another database. And the color of the tag isn’t shown until you’ve actually added the tag to the document.