The map colours represent the following status levels:
sehr niedrig (red): very low status
niedrig (orange): low status
mittel (lavender): medium status
hoch / sehr hoch (green): high / very high status
(Grey represent non-residential areas, while non-built up areas such as parkland and forest are white).
The status levels are based on a combination of "social status" and "social dynamic", calculated on the basis of social statistics (income, rent levels, employment situation etc.). Understandably the outer suburbs are mainly green, while the "problem districts" of southern Reinickendorf, Moabit, Wedding, northern Neukölln and parts of Kreuzberg are red.
The inclusion of a "social dynamic" factor in the calculations means, interestingly, that the orange areas are undergoing a positive development from a low level. This is particularly true of southeastern Kreuzberg, which was red on last year's map.
More detailed information is available from the city website here (German only).