Monitors must be adjusted (calibrated) before their colour balance is accurate enough for professional printing. Simply unpacking the box and plugging them in will not give accurate colour.
- Here's a good first step - and it's easy: open a blank page in your graphics software and hold up a piece of white paper next to the screen. You'll notice that the white of the display is far, far brighter than the white of the paper - turn down the brightness of your display until you get close to the brightness of the white paper.
It's obvious really - the brightness of the screen must match the brightness of the paper you're printing onto - otherwise what you're seeing is completely false.
You'll find that the screen is now quite dark (in fact you'll think it's over-the-top) - but you'll be surprised at how, with this simple adjustment, your screen now comes much closer to matching the printed product.
For more detailed information Colorwiki is a good place to start and there's also an excellent set of calibration images available here.
If colour balance is vital why not, as a test, print a palette on a postcard? You can then see the print quality and colour balance for yourself and you can build up an entire library of colour cards for future reference that you know are 100% accurate (it's what professionals do).
NOTE: monitors change over time so calibration must be checked at least once a year - more often if you're trying to maintain a professional standard.
IMPORTANT: mobile operating systems don't yet support colour profiles - please do not use phones or tablets to check colour balance!