Your Apple Macintosh comes with a very cool feature called ColorSync. If you are using your Mac for graphics work, you are probably already familiar with the ColorSync concept.
ColorSync will ensure that what you see on a ColorSync enabled monitor and what's being printed on a ColorSync enabled printer will look exactly the same.
ColorSync support is controlled from the ColorSync preference pane. Use the OmniGraffle | Preferences... menu command to open up the preference panel.
If you enable ColorSync by checking the Use Color Profiles checkbox, the program will save color profile information along with the OmniGraffle document—or any of your exported graphics files.
If you try to import graphics files that have embedded color profile information, OmniGraffle will use this information accordingly. The same applies if you open an OmniGraffle document that is color profile enabled. You can control what OmniGraffle will do in these circumstances by using the drop-down menu...