The inquisitor’s blade is red, yes. But Skoll’s and Hati’s blades are orange.
Firstly, that was a Nightsisters temple. If you’ve seen the Clone Wars and/or played Jedi Fallen Order, you’ll know who they are. It appears Morgan is one of the few surviving Nightsisters.
Given that the Nightsisters use the Force as magic, I interpreted that scene as Ahsoka sensing the solution through the Force. It’s entirely possible that it was meant to be easily solvable by any reasonably powerful Force user.
Secondly, I am assuming that neither Morgan, Skoll, Hati, nor even Thrawn (this show’s main crop of villains) hid that star map ball in that temple. I presume that thing is ancient and has been hidden away there for a long time.
My guess is that Morgan figured out where Ezra sent Thrawn via the purrgil (a space whale like the one briefly glimpsed by Skoll in the clouds and also by Grogu in the latest Mandalorian season), and then she figured out that her Nightsister predecessors happened to have a map to that location. (Hopefully this will be explained more as the series continues, but so far I’m not finding it quite as contrived as Luke’s map in TFA.)