Whaaaat? What kind of question is that? It implies you even let your skis touch a green run at all.
I don't let my skis get within sniffing distance of a green run. If the only access to where I need to get is a green run, I take off my skis and walk it.
Once when I was at an unfamiliar resort, I found I had accidentally skied part of a green run. Thought about giving away that pair of skis at that point, but ended up deciding to just give them a thorough base grind instead. They still haven't skied the same way since though.