The enforcers don't call it anything in particular, the zones are our invention.
The penalties aren't anything really terrible, ususally just a telling off. But periodically our whole year level is taken aside for a stern talk, because we continue to ignore the rule. Occasionally individual people have been screamed at, but that's rare.
It's just that piece of plastic that joins two sections of carpet together, in a doorway for example. It is possible, if the feet are placed heel-to-toe, for two people to stand on the zone itself, facing each other and leaning against the door frame, but often there's about 6 of us, so we sit in our own zones and just have a toe or something in the purple zone.
One of the more ridiculous rules of my boarding house forbids girls of different year levels being in each others' upstairs areas, invitation or no. The year eleven area and the year twelve area share a doorway (in fact, it is necessary to walk the length of the year 11 floor to get to the year 12 rooms). The purple zone is the thin plastic greyish-purple strip joining the red zone (the year 12 floor with red carpet) and the blue zone (the year 11 floor with blue carpet). This is where we meet to chat.
Edit: It is probably pertinent to add that we do have common areas, but they are two flights of stairs away and most of our chats take place when the year elevens are confined to their floor because they're meant to be getting ready for bed.