The Yellow and Brown areas are fully colonized areas of San Miguel. Maids, gardeners, Cantera Marble, old doors, Mercedes, WIFI abound.
The Beige areas are being colonized. Expats and Expat houses are found dotted through the area.
Most tourists never leave El Centro (the Brown Area). The restaurants, shoppes and Gangs are all there. There is no reason to leave the comfort of North America and wander elsewhere. You can almost tell where El Centro ends and know that something dangerous lies beyond that point.
Occasionally, some Tourists decide to cross the line and enter a Gringo Free Zone as these Tourist have done in San Rafael.