Printers use cyan (C), magenta (M), and yellow (Y) colored ink plus black (K) colored ink to print in full color.
If equal proportions of the three CMY colors are mixed, in theory, pure black should be produced. In practice, the resulting printed color is not pure black and has an inferior feel due to the limitations of printing. In order to reproduce a distinct black color, normally black ink is used when printing color images.
For example, a cyan image can be printed using only cyan ink without any complications; however, a full color image can be made up of over 16 million subtlety different colors. These complicated colors are produced by translating them into proportions of CMYK ink dots per unit area.
In addition, the same color in an image can have lighter and darker parts. These shades of color are produced by varying the amount of ink dots per unit area.