Blue pins mark places of hittakuri (ひったくり) – grab-and-run type of robbery against pedestrians or cyclists.
Red pins mark places of crime or abuse against children (子供被害). Their severity differs and sometimes even “stranger speaking to a child” gets qualified as a crime en par with public obscenity (公然わいせつ) or physical abuse (チカン).
Green pins stand for robbery (強盗).
Apparently it seems that my close neighborhood which is supposedly one of the most dangerous places in Japan observes rather low incident rate. Or they get unnoticed.
According to the software producer, the service is planned to be extended to other prefectures in Japan. At this moment, different cities have their own websites, like for example Tokyo crime map (update: no longer available).