on this subject.
When you see colours on your screen you're seeing radiated colours - they appear rich and vibrant because the screen is illuminated. The colour on the paper that comes out of the printer is reflected colour - what you see is the light that's being reflected by the inks on the page, and they don't always match what you saw on the screen.
The reasons for this are many and complex, and there's not enough space to discuss them here. Suffice it to say that the problem can be solved, and if you click here you'll be able to read a good introduction into the ways and means of doing it.