I think that you are mistaken about what happened on your S950!
As far as I know, when you load a registration bank on any PSR-S or Tyros model, all buttons that contain data will be lit green (or blue), but no button will be selected or lit red! You must press one of them to activate the registration, at which point it will turn red and if you have memorised that registration with a style section and/or multi pad set to sync start, their buttons will flash red.
I assume that this is the same on Genos, although as StuartR has said, if you add a registration bank to a Playlist, you can set one button to activate on loading by editing the Playlist record. Genos is the first model to feature this function!
Regards
Ian