Web Design in a Nutshell, 3rd Edition

RGB Color

Computer monitors use the RGB color model to display colors. RGB color combines red, green, and blue light (thus, RGB) in various amounts to create a range of colors between black and white. The model is additive, which means the more light you add, the closer the resulting color is to white.

Although all monitors use the RGB color model, the actual hues of red, green, and blue light vary from monitor to monitor. This means that even specific RGB colors that are identified numerically may look quite different on different machines. As a web designer, you need to allow for a certain amount of variation in the way your chosen colors will look to your site’s visitors.