1. The three primary colors refer to the three basic colors that can no longer be decomposed. We usually refer to the three primary colors, namely magenta, yellow and cyan (cyan is not blue, and blue is the mixed color of magenta and cyan).
 2. The three primary colors can be mixed into all colors, and they can be added into black at the same time. Black, white and gray belong to the colorless system.
 3. Three primary colors of pigment (CMYK): magenta, yellow and green (sky blue).
 4. The three primary colors of color can mix all the colors of pigments and add them together to form black. Black, white and gray belong to the colorless system.
 5. Optical primary colors (RGB): red, green, blue (indigo).
 6. After the optical three primary colors are mixed, the display screen displays the color. The three primary colors are added together to form white. White belongs to one of the colorless system (black, white and gray).