The details of colors used for radio signal propagation maps with their associated signal levels have been explained here. The colors gradient used is based according to the natural color spectrum of the visible light.

The colors specified in the coverage maps represent the radio signal levels as:

1. Red – Signal level above 60 dBµV/m (>60dBµV/m): In this level (or area covered), the radio receiver (at the ground level) is able to easily tune in to the specific frequency with almost no static noise and interference from other radio broadcasts. Comfortably tunable on all properly functioning types and quality of FM radio receivers.

2. Green – Signal above 48 dBµV/m (>48dBµV/m, <60dBµV/m): In this level (or the area covered), the radio receiver (at the ground level) is able to tune in to the specific frequency with some static noise and a little interference from other radio broadcasts. All types and quality of receivers are able to be comfortably listened to.

3. Yellow – Signal above 30 dBµV/m (>30dBµV/m, <40dBµV/m): In this level (or the area covered), only the radios with high sensitivity are able to pick the signals of the specific frequency at ground level (typically higher quality radio receivers). An additional external antenna (at some height) or the placement of the radio at some height (2^nd/3^rd floor) is required for reception of signals by poorer quality radio sets at this level. The signals at this level will have some static noise and high interference from other radio broadcasts.

4. Blue (Light/Dark) – Signal below 30dBµV/m (>18dBµV/m, <30dBµV/m): This level is highly affected by the atmospheric and terrain conditions and hence is most weak and unreliable range of signal level in radio signal transmission. The signal in this range is easily absorbed by humidity, refracted by the atmospheric layer as well as highly affected by the air temperature and the status of the surrounding terrain.