Each and every color cell is in itself an proper Action, so it can have its own ShortCut.

adding screenshot again..(why this one has problem ?)

It Highlights, no Tags.
it is there in top Tabs row always, not disappearing.
It goes any segment(s) including Source segments

Step 1 "Drag" block you want to highligh
Step 2 "Click" color cell you want to.

That's it.

Note: I'm writing this comment for your (RWS) reference. Should you implement this functionality, pls make just like this.

Eva Repolusk-Stoppel, Andrew James Wood, Lydia Simplicio, Angela Sigee

This new plugin may be of interest here:

https://appstore.sdl.com/language/app/wordlight/1026/

I implemented Word-style highlighting in my Wordbird plugin, downloadable in the AppStore