Colonies adapt the state religion of their overlord and not the dominant faith. That's coded in the on_action on_colonist_boosting_colony
Or are you talking about colonial nations? That's probably hardcoded and can't be changed by a mod. But maybe there is an on_action which happens when a CN is created(e.g. on_country_released or on_colonial_type_change) where you could change the state religion afterwards. Or you could create an event(or a decision which gets automatically clicked by the AI) to change the state religion