Zone Classification Scheme
Green
The official classification for a Green zone is any area with no layers built above it.
"Blue skies above, green ground below, the view from the Green Zone spires is impressive. They reach miles above the surface of the Urban and pierce through clouds, for someone standing down at the surface of the Green Zone they would appear to reach up into infinity. And a few do, a few are built around the massive mass drivers that launch people and goods into space, towards the orbital facilities and the spartan off-world colonies. It's a place of politics and leisure, the skies are crowded by flying vehicles and flocks of birds, the people are wearing the newest fashions and it's rare to see anyone without a smile on their face. After all, how could anyone be sad when they know what hardships they're avoiding by living at the top, literally, of society?"
Blue
The official classification for a Blue zone is any layer that has water which suffers from no discolouration.
"Like being halfway down a canyon made of metal, that's one way to describe the Blue Zones, you're under the surface, but at least you can see the sky almost anywhere, and the water's still clean. Compared to the layers below, life here is still leisurable, and largely lived by executives and intellectuals. Control maintains a minimal presence, but crime is limited and private security firms handle most pressing issues. Gardens are rare, but present, and large plazas have been carved out that permit the citizens to bask in the sun at noon, leading to a common tradition of mid-day siestas permitting people to make the most of the period where the sun is directly above. Animals are rare, and vehicles start transitioning towards wheeled and tracked rather than purely hover-mobile. It's mostly clean."
Yellow
The official classification for a Yellow zone is any layer that still receives direct sunlight. The unofficial classification is a layer where the water is "merely" yellow.
"If the Blue was halfway up the canyon, the Yellow Zone is at the bottom. Sunlight pierces down through the occasional shaft or hole, but most lighting is artificial. The wide vistas of the green and the broad streets of the blue are replaced with a more urban situation. Despite officially being a place that still receives sunlight, most streets have a ceiling five or so stories up. Personal transport becomes replaced by public, as the narrow streets don't easily permit the passage of both people and vehicles. This is where Control does most of their work, as mutants are rare as chickens' teeth in the Blue and Green, but start popping up in the Yellow. There's also the occasional raid by Brown or Black Zone gangs making use of hidden passageways. Work in the Yellow largely tends towards cubicle or manufacturing work, though nothing quite as backbreaking as the factories of the Brown Zone."
Brown
The official classification for a Brown zone is any layer that has no access to natural sunlight at all.
"The Brown Zone is the warren of tunnels dug into the sides of the canyon. If not for artificial lighting, some gas lit, some electrical, it'd be pitch black. Instead it's a labyrinthine mess of streets where people can barely walk three ashoulder and the ceiling is rarely more than two floors above your head. All surfaces seem constructed from scrap metal or trash compacted by the sheer geological weight of the layers above, though a few do tunnel into natural rock or dirt. Despite the relatively miserable surroundings, people find a way to survive. There's rough manufacturing for the layers above, raiding, scavenging, the occasional enterprising entrepreneur and plenty of people who make a living out of being parasitic, leeching power and water from the layers above. Control would be doing most of its work down here, seeing as it's where the most mutants are, but between the utter impossibility of tracking anyone in the Brown, and the general anti-Control sentiments, their only actions down here are when they move down in force to take down particular troublemakers. The elite Convictors still operate in the Brown, though. Mutant wildlife thrives everywhere."
Black
There is no official classification for the Black zones.
"Even the Brown seems hospitable compared to the Black Zones. Despite the walls being made of compacted junk in most places, it seems primal and untouched. There's no light, no sound of people, just the drip of deep underground water, the occasional, mercifully unidentifiable echo and your own breathing. It smells of decay and blind things that live in the dark, it's the home of undiscovered treasures, mutants so twisted even the Brown couldn't house them, vast lakes full of pale white cave fish and things yet undiscovered. It claims an unsurprising amount of Brown and Yellow treasure hunters every year. But there's always a story about someone who struck it rich, someone who found something lost by one of the Green noble houses, or desired by a Blue research firm, so the adventurers keep coming."
Red
Red zones are not zones in the sense of the others, being defined by their horizontal location rather than their vertical.
"A vast shaft carved into the ground, penetrating from the Green surface to the Brown depths, this is a Red zone, a Red area. Crouching in the middle of a field of junk, scrap metal, warning signs and automated defense turrets is a structure that looks more like it was grown than constructed. Like some combination of a vast heart and a titanic nautilus. Cables as wide across as a bus reach from the plant to the walls of the shaft, thrumming with power, and the air in the entire pit is at a constant boil.
The structure is one of the hundreds of geothermal plants constructed decades back, they provide power and, from their penetration of the mantle, raw materials. Their functioning is a closely guarded secret maintained by their Green owners and their Blue inventors, and no one born in the Yellow or below is even permitted to work in one. Security is heavy enough that even the dumbest gangs have learned not to try attacking them for salvage, though a few of the hardier or stealthier scavengers tunnel into the sides of the shaft at Brown level to sneak across the surrounding killing fields and hunt for any leftover materials from the plant's construction."
