embryodead
Caliph
Only tNormalAreas are used for stability. tCoreAreas aren't used but they seem to be the same as 400+ threshold (though someone mentioned America as an exception). Still, I'm fairly sure contested area is checked by normal areas, not core (lines 640-656).
Resurrection uses normal areas as well.
As for 150+ for contested, see line 647. There's a penalty for every city in another civ's tNormalArea - it's -1 if it's also your 150+, -3 otherwise.
I can't seem to find the penalty for settling/owning a city in enemy core (other than the above, which is kind of like it, but doesn't check core). This is why I assumed that enemy normal area and < 150 is "Red" zone. Core area (400+) only seems to be checked for OwnedCitiesLastTurn, but that's supposedly the penalty for losing "Dark Green" cities.
Resurrection uses normal areas as well.
As for 150+ for contested, see line 647. There's a penalty for every city in another civ's tNormalArea - it's -1 if it's also your 150+, -3 otherwise.
I can't seem to find the penalty for settling/owning a city in enemy core (other than the above, which is kind of like it, but doesn't check core). This is why I assumed that enemy normal area and < 150 is "Red" zone. Core area (400+) only seems to be checked for OwnedCitiesLastTurn, but that's supposedly the penalty for losing "Dark Green" cities.