In short, printers and monitors produce colors in different ways. Monitors use the RGB (red, green, blue) color model, which usually supports a wider spectrum of colors. Printers use the CMYK (cyan, magenta, yellow, black) color model, which can reproduce most - but not all - of the colors in the RGB color model. Depending on the equipment used, CMYK generally matches 85–90% of the colors in the RGB model. When a color is selected from the RGB model that is out of the range of the CMYK model, the application chooses what it thinks is the closest color that will match.
