Three color principle in printing color

In the middle school physics class, we may have experimented with a prism. After passing through the prism, white light is broken down into a chromatogram with gradual transitions of multiple colors. The colors are red, orange, yellow, green, cyan, blue, and violet. This is the visible spectrum. . Among them, human eyes are most sensitive to red, green and blue. Human eyes are like a system of three-color receivers. Most of the colors can be synthesized by different proportions of red, green and blue colors. The vast majority of monochromatic light can also be broken down into three shades of red, green and blue. This is the most basic principle of colorimetry, namely the principle of three primary colors. The three primary colors are independent of each other, and neither of the primary colors can have the other two colors synthesized. Red, green and blue are the three primary colors, and the three colors have the most extensive range of colors. The addition of red, green and blue primary colors in different proportions is called additive color mixing.

Red Green = Yellow Green Blue = Cyan Red Blue = Magenta Red Green Blue = White

The yellow, cyan, and magenta colors are made of a mixture of two colors and hue, so they are also called additive secondary colors. In addition:

Red Cyan = White Green Magenta = White Blue Yellow = White

So cyan, yellow, and magenta are red, blue, and green complementary colors, respectively. Since each person's eyes have different perceptions of the same color, if we mix with three primary colors of the same intensity, assuming that the intensity of white light is 100%, then subjective feelings of people are that the green light is the brightest. Red light is the second and blue light is the weakest.
In addition to the additive color mixing method, there is a subtractive color mixing method. Under white light, cyan pigments can absorb red and reflect cyan, yellow pigments absorb blue and reflect yellow, magenta pigments absorb green and reflect magenta, that is:

White - Red = Cyan White - Green = Magenta White - Blue = Yellow

In addition, if the two pigments, cyan and yellow, are mixed, and the white light reflects, the pigment absorbs red and blue and reflects the green color. For the mixing of the pigment, we express the following:

Pigment (Yellow Cyan) = White - Red - Blue = Green Pigment (Magenta Cyan) = White - Red - Green = Blue Pigment (Yellow Magenta) = White - Green - Blue = Red

All of the above are subtractive color mixing, and subtractive color mixing is to form different colors by absorbing different proportions of three primary colors. Therefore, cyan, magenta, and yellow are called three primary colors of pigments. The color mixing of three primary colors of pigments is widely used in painting and printing. In the three primary colors of pigments, the red, green and blue colors are called subtractive secondary colors or secondary colors of pigments. In subtractive secondary colors, there are:

(Cyan Yellow Magenta) = White - Red - Blue - Green = Black

The color mode represented by the above additive three-color primary colors is called RGB mode, and the color mode represented by the principle of subtractive primary colors is called CMYK mode, and they are widely used in the fields of painting and printing.
RGB mode is a color mode most commonly used by graphics software. In this mode, it is more convenient to process images. Moreover, RGB images stored are smaller than CMYK images, which can save memory and space.
The CMYK mode is a paint mode, so it belongs to the print mode, but it is essentially the same as the RGB mode, except that the colors are produced in different ways. RGB is the additive color mixing mode, and CMYK is the subtractive color mixing mode. For example, the display uses the RGB mode because the display is a beam of electrons that bombards the fluorescent material on the screen and emits bright light to produce color. When there is no light, it is black, and when the light is maximum, it is white. What about the printer? Its ink does not emit light by itself. Therefore, it is only necessary to use a subtractive color method to absorb the color of the other light by absorbing the specific light wave.