Spot color refers to a specific color. When printing, spot color is not synthesized by printing C, M, Y, K four colors, but is specially printed with a specific ink. Spot color ink is pre-mixed by the printing plant or produced by the printing plant. For each spot color of printed matter, there is a special color plate corresponding to it when printing. Use spot color to make the color more accurate. Such as: special gold, special silver, etc. Four colors refer to CMYK mode printing colors.