A novel diffractive CIE 1931 chromaticity diagram is generated by utilizing surface relief gratings on a plastic sample. A properly illuminated sample is shown to reflect the CIE chromaticity diagram with exact colors and large gamut. Additive color mixing is accomplished by utilizing the four main peaks of a 4000 K fluorescent lamp's spectrum as the primary colors. The primary grating units are reflecting the combination of the primary colors to the desired viewing angle and thereby forming the correct chromaticity (x, y) at each pixel of chromaticity diagram. Weights of primary colors at each pixel of the diagram are controlled by fixing the relative areas of the primary gratings. The master grating is fabricated with aid of electron beam lithography. The final grating is hot embossed on a polycarbonate sample using an electroplated nickel shim. Chromaticity values are measured from the plastic sample by a spectroradiometer. (c) 2007 Wiley Periodicals, Inc.