Abstract: A method of forming a polymeric building product having a color variation simulating natural building material includes introducing base color pellets having a base color into the barrel and providing a plurality of first colorant shots and second colorant shots. The first and second colorant shots are repeatedly introduced to the base color pellets in an alternating pattern. By repeatedly introducing at least one first colorant shot and at least one second colorant shot to the base color pellets in an alternating pattern, the barrel is in a constant state of purging. As one melted colorant shot is purged and replaced by another melted colorant shot, the melted composition includes streaks in the shape of swirls, wisps, etc., which advantageously creates color variations that simulate natural building material.