Underfire
I assume you got the coverage maps here:
ADS-B coverage | Airservices
It would seem that the different colour areas have specific meaning. However, I cannot find any sort of legend. Which makes me suspicious that its more a sh1t & glitter exercise than a genuine effort to impart information.
Do you know what the colours might mean? I'm also a bit suspicious of these maps. They look very like the ones Telstra produce for mobile coverage or AsA produce for VHF coverage. I've had ATC ring me in flight on my mobile because they could not reach me of a nearby QantasLink flight on VHF