The Sindome social classes help make the game interesting by dividing the city into 4 distinct physical levels based upon the economic class of that level's 'common' denizens.
BLUE - The rich and powerful live and play here. Most likely, if they work, they work on the GOLD level. Crime is low and the places are nice.
GREEN - The Middle Class, the working man. Crime here is relatively low and you might even have a nice place, nothing too fancy though.
GOLD - The Corporate Zone. This place is home to all the headquarters of the major corps along with the main city building, the Withmore Hall of Justice. Corporate security ACDs patrol the area while aerodynes buzz around like they have a place to go.
RED - The red sector, can we say low class? I thought so. Life down here is on edge, with the city prison's population control failing along with its security on occasion. Honest...it's rare, but how can crime not help to be high? Life is gritty, but people get by.
Traveling from level to level is easy at some places and hard at others (depends on the security). As you move about, you'll notice differences, with stuff as simple as the currency people use. We have chyen (hard currency) and cred chips (like a credit card). Places on the GREEN level (the few there) will take both most likely, as will places on GOLD, but BLUE ain't taking your filthy chyen and RED can't afford to get the cred chip validators. These are just a few of the examples, but I'm sure you get the idea.