How to profile dual monitors on OS X.

While it is always best to use two separate video cards when using a dual display setup, the Mac OS X system does work a bit differently and usually can handle the 2 profiles for the individual monitors.   Keep in mind that any time that you are connecting two displays on a single operating system, while the system itself can handle the displays they can not always handle two profiles being utilized at the same time.  To do so you need the following:

- Support for individual Video LUTs (lookup tables) for both monitors (support of two graphic chips)
- Support for handling individual ICC profiles for both monitors

To set up Dual Displays in the Mac OS X:  
(Works the same whether you have two graphic cards or a dual card with two graphic chips and output signals.)
1. Activate the "Multiple Monitor Features" on system level by going to "System Preferences -> Displays" and pressing "Detect Displays".

2. Check the option "Show displays in menu bar".

3. Select the tab "Arrangements" and arrange your displays or you can also choose to Mirror them from this screen.  It is important to note that while you can Mirror the displays you should still profile them individually to allow accurate color to be produced through the video card.  Now you can calibrate and profile each monitor.

4. Start i1Match or the ColorMunki software and move the appearing main window on the monitor, which you want to profile.  ColorMunki Software will allow you to select Display 1 or Display 2 in the default settings.

5. Perform the profiling process and save the profile. It should automatically be set as default system profile.

To check or assign your current monitor profile:
1. Go to "System Preferences -> Displays -> Color".

2. Open "Displays" (if in the option "Show display in menu bar" was activated). A window with a list of available monitor profiles will appear on each monitor. The active profile will be marked.