Regarding detection colors: Each dot on the radar is colored to represent the strength of a single entity and its readings, and if a detection goes outside of radar range, then that same detection returns within the range of the radar, you will close to the same color, or if it is different unique detection, a unique color should appear.
This application is totally safe to download. Ninjetic Studios is the official developer of the app which can be found in the Entertainment category. Over 100K users downloaded Real Ghost Detector and the most recent update was released on Nov 27, 2017.
Google Play displays that this application is rated 3.6 by its users. The app contains advertisements. Download the setup package of Real Ghost Detector 1.9 that is completely free and take a look at users' reviews on Droid Informer.