Color management can automatically convert images from your Photoshop color numbers to your printer color numbers, but automatic conversions won't handle every image optimally. When you squeeze a monitor's wide color gamut and dynamic range into a printer's smaller gamut and range, you have to sacrifice what isn't important in the image. Great prints still take intelligent human intervention. After you understand what color management can do for you, it's time to put it into action. The accuracy of the whole process depends on the accuracy of your monitor and printer profiles .
Profiles describe a monitor's or printer's color space with numbers.
Color management employs profiles to determine what colors the numbers represent and to calculate the new set of numbers you'll send to your printer to make it reproduce those colors. Most of today's vendor-supplied profiles for desktop printers are accurate only if you use the printer vendor's inks and papers, because the printers, ink, and paper are consistent from unit to unit and batch to batch. But monitor profiles are another story. Manufacturing variance, lighting conditions, and user-adjustable brightness and contrast controls conspire to make every monitor unique, and no generic profile will describe your monitor's behavior accurately. If you want an accurate soft proof, you must make a custom profile for your monitor.