Throughout history, reproducing the colors we see in nature has taken many forms. The media and methods used to reproduce color include paintings, printing presses, color file, color monitors, color printers, etc. There are only two basic was, however, of reproducing color – additive and subtractive.
Additive Color System [ RGB ]
The additive color system involves light emitted directly from a source, before it is reflected by an object. Light of a specific color, or wavelength (for example, a theatrical spotlight), can be produced by directing white light through a special filter that allows the desired wavelength to pass blocks others. The additive reproduction process mixes various amounts of red, green and blue light to produce other colors. Combining one of the additive primary colors with another produces the additive secondary colors cyan, magenta, and yellow.
To illustrate this, imagine three spotlights, one red, one green and one blue focused from the back of an ice arena on skates in an ice show. Where the blue and green spotlights overlap, the color cyan is produced; where the blue and red spotlights overlap, the color magenta is produced; where the red and green spotlights overlap the color yellow is produced. When added together, red, green and blue lights produce what we perceive as white light.
Television screens and computer monitors are examples of systems that use additive color. A mosaic of thousands of red, green and blue phosphor dots make up the images on video monitors. The phosphor dots emit light when activated electronically. It is the combination of different intensities of red, green and blue light that produces all the colors on a video monitor. Because the dots are so small and close together, we do not see them individually, but see the colors formed by the mixture of light. Colors often vary from one monitor to another. This is not now information to anyone who has visited an electronics store with various brands of televisions on display. Also, colors on monitors change over time. Currently, there are no colors standards for the phosphors used in manufacturing monitors for the graphics arts industry.
To summarize: Additive color involves the use of colored lights. It starts with darkness and mixes red, green and blue light together to produce other colors. When combined in equal amounts, the additive primary colors produce the appearance of white.
Subtractive Color System [ CMYK ]
The Subtractive color system involves colorants and reflected light. Subtractive color starts with an object (often a substrate such as paper of canvas) that reflects light and uses colorants (such as pigments or dyes) to subtract portions of the white light illuminating an object to produce other colors. If an object reflects all the white light back to the viewer, it appears white. If an object absorbs (subtracts) all the light illuminating it, no light is reflected back to the viewer and it appears black. It is the subtractive process that allows everyday objects around us to show color. Remember the example of the red apple? The apple really has no color. It has no light energy of its own. Colorants in the apple’s skin absorb the green and blue wavelengths of white light and reflect the red wavelengths back to the viewer, which evokes the sensation of red.