When processors and OEMs require NSF 051-certified colors, they need look no further than Plastics Colorโs Colors Now App. A group of six shades of gray and white matched in polypropylene are NSF 501-certified, according to Sarah Skidmore, additives product line and marketing manager. NSF International is an accredited, independent third-party certification body that tests and certifies products to verify they meet these public health and safety standards.