Shades of blue pigment blue, is the tone of blue that is achieved by mixing process (printer's) cyan and process (printer's) magenta in equal proportions. It is displayed at right. The purpose of the CMYK color system is to provide the maximum possible gamut of color reproducible in printing by the use of only three primaries. The color indicated is only approximate as the colors of printing inks may vary. The color defined as "blue" in the NCS or Natural Color System is an azure-like color shown at right (NCS 2060-B). The Natural Color System is a color system based on the four
C-41 process not is a subject of some debate. C-41 film consists of an acetate or polyester film base, onto which multiple emulsions are coated. Each layer is only sensitive to a certain color of visible light. In the classic illustrative example, there are three emulsions: one is red sensitive, another is green sensitive, and the top is blue-sensitive. Beneath the blue layer is a yellow filter, composed of dyes or colloidal silver. All silver-based photographic emulsions have some sensitivity to blue light, regardless of what other colors they may be sensitized for. This filter layer serves to remove the blue light,