Perhaps you should calibrate your monitor to your printer. Depending on how your monitor is set up will determine what you see on screen. If you are using true color management software your printer should print the color you indicate, however if you are depending on the visual color on your screen, that is not going to register as true unless your monitor is calibrated to your color management system. As far as your monitor knows, red is red, however, your printer when building PMS Red 400 (or whatever) is getting that particular receipe from the color software. Monitor color is RGB, print color should be CMYK.