Abstract: Control of Hunter A and B color values of fiber-grade polypropylene compositions having a stabilizer additive system therein is achieved by processing the polypropylene and additive system in an atmosphere having an oxygen content in the range of 0.1 to 5.0 volume percent. Desired color of the processed polymeric composition is maintained by monitoring the color of the pelleted product and, responsive thereto, controlling oxygen content of the mixer atmosphere or by measuring the oxygen content of the atmosphere of the mixer and maintaining same within a predetermined concentration whereby the color of the pellets is maintained within a predetermined range.