RGB color model

Additive color mixing: adding red to green will yield yellow; adding yellow to blue will yield white.

The RGB color space is an additive color space which models the way light of a few specific frequencies are combined when travelling in the same direction. RGB is known as an additive color space because when light of two different frequencies travel together, from the point of view of an observer, these colors are added to create a new color experience. In particular, the colors which the RGB color space concerns itself with are the red, green and blue frequencies (hence the abbreviation RGB). These three frequencies are chosen because each one corresponds roughly with one of the three types of color-sensitive cones in the human eye. With the appropriate combination of red, green and blue light, one can reproduce many of the colors that can be experienced by a human. For more information on how humans perceive color, see the entry on color itself.

One common application of the RGB color space to display computer graphics on a monitor. For each pixel in the image, independent values for red, green and blue are stored. There is a fixed range of red, green and blue intensities displayable by the computer monitor, but by choosing the appropriate combination of red, green and blue light, one can stimulate in the human eye the perception of many of the colors between the black level and white point of the monitor being used to display the image. Typically the values stored vary between zero and 255.

As an example:

• (0, 0, 0) is black
• (255, 255, 255) is white
• (255, 0, 0) is red
• (0, 255, 0) is green
• (0, 0, 255) is blue
• (255, 255, 0) is yellow
• (0, 255, 255) is cyan
• (255, 0, 255) is magenta

It is important to note that the intensity of the color output on computer display devices isn't always linear. That is, even though a value of 127 is very close to halfway between zero and 255, the color output of a computer display device when displaying (127, 127, 127) is significantly lower than halfway between the black level and white point of your monitor. This is because most display devices have a gamma characteristic different from 1 (i.e. the behavior of most display devices is, unfortunately, not linear in the relationship between color value and output intensity), and require gamma correction.