Works like this:
Code:
barracks_1_barbarian requires factions { barbarian, thrace, }
and building_present_min_level hinterland_culture_barb barb_colony_1
Code:
barb_colony_1 requires factions { barbarian, }
or factions { thrace, } and not building_present hinterland_culture_west
Basically, if you want to build yourself a barbarian colony, you can't have a western culture base present. I know it's made a little bit difficult with the fact that you can't destroy the colonies, so you're stuck with either western or barbarian. I'll try to make it less inhuman for the next release, so instead of having trouble with colonies, you just won't be able to have 2 types of barracks at once. Sorry for the confusion.