Having been in a light blue unit turned purple with the addition of green, I experienced the cultural gap at first hand. A preponderance of lt col were woefully out of their depth regarding blue.
It may be true that junior officers brought up in a joint environment can integrate successfully but at the operational command level I think the culture difference would cause difficulties. Even role changes at command level inspire distrust and unease. Some commanders manage, some don't.
Ask why the Canadian experiment failed.