RGB Model:

The RGB model is depend on the assumption that any desired shade of colour may be obtained by mixing the correct amounts of red, green, and blue light. The exact hues selected are not important as long as they include a long wavelength hue (red), a medium wavelength hue (green), and a short wavelength hue (blue). If, for instance, circular red, green, and blue beams are projected onto a white screen in a darkened room, we get the colour pattern illustrated in Figure.

The additive nature of the RGB model is extremely clear in Figure. Adding red, green, and blue light generates white light, while adding up red and blue light produces magenta light, and so on. This linear superposition is expressed mathematically as following:

                                  C = rR + gG + bB

where, C = colour of resulting light,   Visual Realism

 (r, g, b) = colour coordinates,

 (R, G, B) = red, green, blue primary colours.