Why are the three primary colors of light different from the three primary colors of pigments, and they are complementary after being superimposed on each other?

The principle is different. For light sources, the effect of color superposition is to show the color effect of each light source at the same time, such as red+green, and the result is yellow. For objects, the effect of color superposition is to display the color reflected by each color. For example, yellow objects reflect more red and green light, while blue objects reflect more green, blue and purple light. Together, they reflect the same color, which is green. Therefore, the color superposition of light sources will become brighter and brighter, and the color superposition of pigments will become darker and darker. In addition, whether the color of the light source is pure or not is only related to the light source itself. For example, a red light source, whose color is red, will not change color no matter what environment you put it in. But the color of pigment is not pure, and it is also related to the surrounding environment. Anyone who has studied art will know that these are "inherent colors" and "environmental colors". ) Three primary colors and three primary colors actually mean the same thing. That is to say, in theory, if three colors can be combined into any other color, then these three colors are three primary colors or three primary colors. From the principle of color mixing, it can be generally divided into three optical primary colors (following the principle of color addition) and three printing primary colors (following the principle of color subtraction): the color of red, green and blue: red+green = yellow; Green+blue = cyan; Red+blue = magenta; Red+green+blue = white (white) All the colors written here are the superposition of 100% colors. With their different superposition ratios, different primary colors are produced: cyan, magenta and yellow: cyan+magenta = blue; Magenta+yellow = red; Yellow+green = green; Cyan+yellow+magenta = black. The color written here is the superposition of 100% color. Different colors are produced by their different superposition ratios. Because printing uses the principle that ink reflects light to produce color, the purity of reflected color has a great relationship with the ink used, especially cyan Huang San color is superimposed into black, which can not reach pure black in practical application, so a kind of black will be added in printing to form cyan yellow and black. Television and display are the three primary colors of optical principle, and the color is produced by the superposition of three colors with different amounts. Books, posters and other printed materials are all made by using the principle of subtractive color. Because of the different color forming principles of optical color and printing color, the color gamut they express is also different. Generally speaking, the optical color gamut includes the printing color gamut. This is why the color of printed matter sometimes does not reach the color displayed on the monitor or TV set. In addition: among the three printed colors, cyan refers to sky blue, and magenta refers to magenta and rose red. In early printing houses, workers were generally called blue and red. Therefore, this resulted in three colors of printing: red, yellow and blue. This is confused with optical red, green and blue. So we must pay attention to this.