Apple AppleVision monitors (OS 7.1) - Manual (Page 33)

The Custom Gamma Curve dialog box appears.
3 Click the Preview Gamma Effect box to preview the effects of your changes as you make
them.
4 Change the gamma setting by moving the crosshairs or typing in a new value.
5 Click Save.
6 Enter a name for the setting, then click Save again.
The name will appear in the Gamma Curve pop-up menu so you can use the
setting in the future.
7 Click the Recalibrate button to calibrate the monitor to the selected color settings.
33 Color Settings
Drag to change
gamma.