a method of making plastic materials , such as plastic lumber , wherein recyclable plastics are sorted into at least two categories and the recyclable plastics in each category are then shredded and chipped , extruded , and mixed with selected colour concentrates to produce the plastic materials of a selected colour . this invention allows for the control of the selected colour to enable replication of such colour of the plastic materials , regardless of any variation in colour of the recycled plastics in each category .