Adjust your external monitors' built-in controls from the OSX shell:
- brightness
- contrast
And possibly (if your monitor firmware is well implemented):
- input source
- built-in speaker volume
- on/off/standby
- rgb colors
- color presets
- reset
make install
For an On-Screen Display using OSDisplay.app:
make CCFLAGS=-DOSD clean ddcctl
Run ddcctl -h
for some options.
ddcctl.sh is a script I use to control two PC monitors plugged into my Mac Mini.
You can point Alfred, ControlPlane, or Karabiner at it to quickly switch presets.