-display display
This argument allows you to specify the server to connect to; see X(7).
-screen screen
When multiple displays are configured as a single logical display, this option allows you to select the screen you wish to change.
-quiet
Silence the normal output of xgamma
-help
Print out the `Usage:' command syntax summary.
-gamma f.f
The gamma correction can either be defined as a single value, or separately for the red, green and blue components. This argument specifies the gamma correction as a single value. If no value for the gamma correction is given xgamma returns the current gamma correction of the display.
-rgamma f.f
This argument specifies the red component of the gamma correction.
-ggamma f.f
This argument specifies the green component of the gamma correction.
-bgamma f.f
This argument specifies the blue component of the gamma correction.