First thing, unless you have a high end monitor that is calibrated on a regular basis, you should never trust your computer monitor for color and saturation. You need to preview your work on a broadcast monitor for best results. If you do not have the funds for that, then a HDMI to a regular LCD tv will give you a better idea of your final result, or even a Firewire output will do.
It may be a matter on how your footage is compressed – the graphic elements are created in the computer, no compression, your keyed footage is probably compressed, so when you compress for final delivery they will look different. My suggestion is to look at your footage in Color Finesse and see the saturation of your colors.
Tudor “Ted” Jelescu
Senior VFX Artist