How to make a mob have a "hidden name" but have a different, visible name?

I have an automated display in my freebuild world that spawns a shower of jeb_ (rainbow) sheep who die after 30 seconds. I summon them in and kill them with command blocks but are there any commands to spawn them with a "hidden" name and "visible" name? e.g a sheep appears to be called Johnson to any players looking at it but has the rainbow effect of being called jeb_.

You can't do this, as the name "jeb_" is built into the game, and is not a command. An alternative I can suggest is repetitively changing the sheep's wool colour by killing the current colour and spawning the next colour after that one, and doing it over and over.

This, however, will break after the DataID removal in 1.13 as it is a major update to commands.