If you want the image that comes from your printer to match what you see on your screen, you’ll need to do some basic color management.
To do that, you’ll need to calibrate your monitor. Without a good monitor calibration, there can simply be no color management. The monitor calibration is the starting point for every good-looking print.
There are several different hardware/software products available to you for monitor calibration. They all essentially work the same way. You attach a colorimeter to your monitor, then you run some software that takes your monitor through a series of tasks, recording the results.
Since Aperture will rely on the monitor calibration to tell it how the colors on the screen should print, it has to know how those colors are recorded. That’s why calibration is so important.
One note here. All Macs ship with a utility in the System Preferences Folder that will allow you to perform a simple monitor calibration. Use this if you just can’t afford the extra hardware. It’s better than nothing, but you’ll get closer if you use a colorimeter.
Here’s another tip. Be sure to calibrate your monitor under the lighting conditions that match the way you work. If you work (God Forbid!) under florescent ceiling lights, then calibrate under florescent ceiling lights.
Also, repeat this process about every four weeks (if you have a CRT) since the phosphors in your monitor fade over time. This causes the color on your monitor to shift. If you use an LCD monitor, repeat every three to six months.
You probably won’t notice any change in color by your naked eye, since these changes aren’t obvious if you look at the same monitor all day, every day. But over time, it will cause your profiles to go out of sync if you don’t re-calibrate.
Select an ICC profile that matches your printer, ink and paper. In order to do this, you will need to create, download or buy a separate profile for each ink/paper combination that you use. It is not enough to create a generic profile for your Epson 4000, for example. You need to create a profile for Epson 4000 with Epson Radiant White paper and Epson inks, etc. Generic profiles will get you close, but they are no match for specific profiling.
Color management is an advanced topic, but don’t let that scare you. Do the basics. Calibrate your monitor and select matching printer profiles. You’ll probably see an improvement in your prints.