A method of manufacturing a plurality of colors of bulked continuous carpet filament from a single multi-screw extruder which, in various embodiments, comprises: (A) passing PET through an extruder that melts the PET and purifies the resulting PET polymer melt; (B) splitting the extruded polymer melt into a plurality of melt streams and adding a colorant to each of the plurality of melt streams; (C) using one or more static mixers (e.g., thirty six static mixers) to substantially uniformly mix (e.g., homogeneously mix) each of the plurality of melt streams with its respective added colorant; and (D) feed each of the uniformly mixed and colored plurality of melt streams into a respective spinning machines that turns the polymer into filament for use in manufacturing carpet, rugs, and other products.