What is RGB?
Although a computer monitor and a printer are both able to create every color of the rainbow, they require two different approaches to achieve this. The printer relies on a subtractive process where three primary colors of magenta, yellow, and cyan are blended to produce all the others. Because the monitor generates images using light, it requires an additive process using the primary colors of red, green, and blue. To understand more about the nature of light, check out websites like about.com.
Because of the three primary colors used, computer monitors are often referred to as RGB monitors. The monitor actually creates an illusion of additive blending by placing the primary colors next to one another in the form of pixels. The additive method is similar to how the human eye perceives light.
The different approaches between a monitor and a printer require software to make the appropriate corrections. When red, green, and blue light are combined, they produce the secondary colors of magenta, yellow, and cyan. Printers rely on these as the three basic hues used to create full-color images, and the software they use relies on this relationship.
The secondary colors are created by the blending of two primary hues in equal proportions. When red and green overlap with the same intensity, the secondary hue of yellow is produced. The mixing of blue and green create cyan, and the cross between red and blue creates magenta.
After the six primary and secondary hues, the remaining colors are grouped together as tertiary colors. The tertiary hues are generated by varying the intensity of one or both primary colors. Blending all three primary hues in equal amounts creates white light. On an RGB monitor, black is the result of an absence of any light. This method of generating hues, along with lightness and darkness, are employed in all devices that create images using light.