MacOS has had first-class support for file tagging for years: You can add arbitrary tags either from “Save as” dialogs or from Finder, and can then browse by tags in Finder or search through your file system filtered by tags.

Does the native file tagging see much adoption? I'm a lifelong Mac user and tried using the tags when they first launched, but eventually it was too much work and I resorted to using search to find what I'm looking for. Not macOS native search but tools like LaunchBar, Alfred, et al or apps like EasyFind.

Colours, yes – but then again I worked in a print shop that'd been using Apple since MacOS 8, so they might be used to those quirks.

I like tagging for bookmarks in Firefox and derivatives of Firefox.

Sharepoint tries to push people towards tags, but doesn't always succeed.