So, interesting thing I realized? Yellow was chosen as Persona 4's key colour, for a lot of reasons, but one of those reasons was because yellow was associated with warnings and caution, like police tape.
You know what red has a lot to do with? Stopping.
nothing mindblowing, I know, but hey.
Well, in the trailer, everyone had stopped around him while he was turning around. Maybe that'll be the shadow world equivalent, just able to stop time and enter it.