Abstract: Colored polyester plastics produced through the introduction of coloring agents prior to extrusion but after pellet production of the base polymer are provided. As a result, the plastic is melt-extruded and mixed with the coloring agent and subsequently subjected to solid stating wherein the base polymer is accorded an increase in molecular weight and the coloring agent becomes integrated therein. Such a method permits avoidance of introduction of a coloring agent to the polymerization reaction chamber that results in extensive staining (particularly upon a change of desired colors for the next batch of plastic). Such a method also permits avoidance of the introduction of a coloring agent to an injection molding process that results in uneven color dispersion and sub-optimal physical properties within the ultimate article. The inventive procedure produces colored thermoplastics of substantially the same shades and uniformity as with the aforementioned precoloring or masterbatch process.