Abstract: A color grading scale comprises a plurality of individual cast resin chips, each representative of a single color, with the chips attached one to another to form continuous array of color chips. In a preferred form, the chips are incorporated into a linear slide which fits within a groove formed in a surface of a frame. The frame is formed of a plastic material having a bright white color for maximum white light reflection. Formed in the frame adjacent to and spaced from the groove is at least one shallow pocket having a depth substantially the same as the groove for receiving a gemstone to be color graded by comparison to the color chips of the slide. Plural pockets of different sizes may be provided to accommodate different size stones.