The TAPPI T 527 standard specifies the Measuring method for paper and Cardboard Color, using d/0 (diffuse reflection /0 °) geometrical optics and CIE (International Commission on Illumination) C Light source. The method calculates tristimulus values X (red), Y (green), Z (blue) through tristimulus filter colorimeter or spectrophotometer measurement paper reflectance, and can be expressed in a variety of Color Space systems, such as Hunter L, a, b or CIE L *, a *, b *, etc. This standard applies to white or nearly white paper and Cardboard, and is widely used for quality control, product development and Color conformity assessment to ensure the unity of paper and Cardboard in visual effect.