more food for thought ....
Red Zone is an interesting concept. When viewed in the perspective of a car tachometer analogy, it's simply a don't go there area. You can go in there by accident, but you should get out ASAP. When viewed from an engineering mentality, red zone is just beyond the design limit: it's understood that you can operate on there purpose but you have to understand that things could break at any time. When red zone = danger from the skiers perspective (i.e. "a person's RedZone") we get into a gray area where the mix of skill, thrill and experience changes the definition. So it's good the definition is based on reaction to the terrain, but then it becomes hard to define what terrain is dangerous. At the upper levels a lot of a persons orange terrain is pretty dangerous.
I tend to overzone (pushing a student into a zone) some of my students more than many other instructors would. I would think that I'd never push a student into what I would say is their red zone, but it's likely for some rare students I do push them into their personal red zone because of a big difference between my assessment of their skills and their own self-assessment. When I over zone students most of the time my primary intent is to down zone easier terrain for them in order to allow more offensive movements to be used in easier terrain. When students come to me with a lesson goal of being over zoned (e.g. I want to ski my first black), I make every effort to accommodate them.
When we do take students into the orange or red zone, it's the pro's job to put up virtual safety netting. By staying in front, choosing the line, setting the pace, taking breaks, pointing out hazards, giving appropriate feedback, teaching tactics, etc. we can greatly reduce the risks involved.