The four-color printing process typically begins with the creation of four screens, each representing a different color applied to the printed image. These four colors are Cyan, Magenta, Yellow, and Black (CMYK); the "K" stands for black, rather than the letter "B," to avoid confusion with "blue." Each of these colors can be applied to a sheet of paper individually, so that the combination of all four creates the final image. Some modern devices can use a four-color printing process that applies all of these colors simultaneously, rather than passing one sheet of paper through four individual stages.
Essentially, a four-color printing process uses individual layers of color that combine and overlap to create a complete image. The first step in this process is typically for an image to be deconstructed into four screens that represent each layer of color found within it. This was once done on sheets of photographic film, though modern technology allows for digital color separation to be performed using computer software.
The four colors used in the four-color printing process require a separate layer or screen for each one. Cyan is a light blue color, while magenta is a light red that is slightly similar to purple. Yellow is a standard color and between these three, there are numerous other colors that can be made. Magenta and yellow combine to make red, yellow and cyan create green, and magenta and cyan make blue. Black is used in the four-color printing process to allow for additional tones and shades within these combinations.
As a rule, the standard four-color printing process uses individual printing plates or applications of color to make an image. One sheet of paper passes through an application of each color, beginning with cyan, then moving onto magenta and yellow, before finishing with black. Additional applications or coatings can be applied to the paper, often to protect the ink and to give it a glossy appearance. After these colors are applied, then the image is complete and the individual layers of pigment are essentially imperceptible.
Improvements in printing technology, however, has made it possible for a four-color printing process to be performed in a single stage. All four pigments can be applied in one step, allowing them to combine and make an image seamlessly. This process is used to print full, vibrant color quickly for use in commercial applications. Single-pass processing is quite expensive, however, and as a result is not as common as traditional techniques.