Which economic policy was based on the idea that the american colonies is is primarily to provide economic benefits for great britain

It would be the economic policy of "mercantilism" that was based on the idea that the American colonies primarily were meant to provide economic benefits for Great Britain, since this philosophy held that trade between two entities benefits mainly the larger entity (in this case Britain), and that it is in that entity's best interest to protect its trading partner (the colonies). 

Word of mouth.