In short, Colonizations has dependencies on Python 2.3 (or maybe 2.5, or both, nobody seems quite sure at the moment and both seems to be needed for all Civ IV games/mods to play nicely). Yosemite doesn’t ship that old software anymore.
This fix uses third-party Python frameworks/libraries/etc – use at you own risk!
http://pcgamingwiki.com/wiki/Civilization_IV#Failed_Initializing_Python