I'm trying not to think about it to hard, but red lightsaber means sith. I'm sure there a few exceptions, but that is the rule. You assume the current Jedi Order at least learns that.
The red saber is made via bleeding the crystal, and that is a very dark side thing.
https://starwars.fandom.com/wiki/Bleeding
Of course this will make sense, if Mr. Grins kills all the Jedi.