Feature request : highlight single non mapper hex

When trying to map the whole city, it is a bit difficult to distinguish on the map the hex with no coverage when all around hex are covered, certain with a low RSSI.
Would it be possible to have an option to switch all the non covered hex in a visible color like red ; or eventually only the hex with coverage existing around ?

Start by locating the map rendering entry point and the code that determines hex coverage or RSSI. Clarify whether the option should highlight every non-covered hex or only non-covered hexes surrounded by covered ones. Done means the selected map view visibly distinguishes the requested hexes without obscuring existing coverage information.

Written by the indexing model from the issue text.