L, a, B a and b are chromaticity values representing the color of an object, that is, the color space coordinates of the color, and any color has a unique coordinate value; Where L stands for brightness (black and white), A stands for red and green, and B stands for yellow and blue; △Eab is the total color difference (whether it is qualified or not); Where △L: If it is positive, it means that the sample is brighter than the standard plate; If it is negative, it means there is a deviation ...