This is where the zoning idea comes in. It is an overlay over the usual gameplay map. Using the following legend, you can see where you can build, where you should avoid building, and so fort:
Inner border colour
- Black - controlled, no opinion
- White - not controlled by any local authority
- Green - controlled, they like you enough so you can build
- Red - controlled, they don't like you enough to make you build
- Green - you can build in this area
- Red - you cannot build in this area (this is mainly for the case of a local authority actually liking you, but they won't permit you to build motorways or a competitor bought exclusive rights to their area)
Now it is about 3 in the morning. So I am not in the mood for writing that much more yet. I have created any code yet, I'm afraid.
Also, I might could use blue and yellow for "like/dislike" you instead of red and green.