Under system software version 7.0, you no longer need to press the Option
key. Just click the "Option..." button in the Monitors control panel to
display the dialog box.
If you do hold down the Option key when clicking the "Option..." button in
the Monitors control panel, you are presented with an option to "Use
Special Gamma" for applications where accurate color representations are
essential, or in situations where two differernt types of monitors are used
whose colors must match.