I'm guessing that you're describing shades of color here. For example, on the screen you see a nice blue-green, but on paper it comes out too green, or too blue. If that's the case, realize that ink and light work very differently. The brightness of the paper you're printing on will have an effect. Your monitor is probably not calibrated to look like the printed page. And the quality of the printer itself will make a difference. (Econo-printing doesn't give faithful results.)
Do a Google search on monitor calibration for tips on how to do modify your monitor settings to more closely match the output.
