Linux -- Display has red tint

Question

My monitor seems to have a slightly reddish tint when using the DVI input (it's a LCD, not a CRT). On the VGA input I can adjust the colors, but not on DVI. On OSX/Windows what I would do is create a custom color profile for that display with changed gamma/etc settings, but I cannot seem to find out how to do this under Linux.

Is there any way to change the color profile under linux (short of buying color calibration hardware and using dispcalgui)?

Answer 1

Typing xrandr --gamma 1:1:1 will likely fix the problem. This should work on any X11 based display system.

Answer 2

You can try to alter it via software, such as:

$ xrandr --listmonitors
Monitors: 1
 0: +*DP1 3840/600x2160/340+0+0  DP1

$ xrandr --output DP1 --gamma 1:1:1

#or

$ redshift -x -m randr

That will try to reset it to the default values, but if another software like xgamma ran like this:

$ xgamma -rgamma 1.0 -ggamma 0.6949030005552019 -bgamma 0.4310480202110507

then the above xrandr won't reset it(because xgamma is using vidmode not xrandr mode, see below), so instead you'd have to use:

$ xgamma -gamma 1.0
-> Red  1.000, Green  0.695, Blue  0.431
<- Red  1.000, Green  1.000, Blue  1.000

to reset it, or $ redshift -x -m vidmode (see below)

It depends which functions each program uses behind the scenes. But the point is, you can use different number values for Red, Green and Blue with such programs and try to remove the red tint.

There's also redshift to change the color temperature in Kelvin or the R/G/B gamma colors just like the above two programs:

$ redshift -h
Usage: redshift -l LAT:LON -t DAY:NIGHT [OPTIONS...]

Set color temperature of display according to time of day.

  -h            Display this help message
  -v            Verbose output
  -V            Show program version

  -b DAY:NIGHT  Screen brightness to apply (between 0.1 and 1.0)
  -c FILE       Load settings from specified configuration file
  -g R:G:B      Additional gamma correction to apply
  -l LAT:LON    Your current location
  -l PROVIDER   Select provider for automatic location updates
                (Type `list' to see available providers)
  -m METHOD     Method to use to set color temperature
                (Type `list' to see available methods)
  -o            One shot mode (do not continuously adjust color temperature)
  -O TEMP       One shot manual mode (set color temperature)
  -p            Print mode (only print parameters and exit)
  -P            Reset existing gamma ramps before applying new color effect
  -x            Reset mode (remove adjustment from screen)
  -r            Disable fading between color temperatures
  -t DAY:NIGHT  Color temperature to set at daytime/night

The neutral temperature is 6500K. Using this value will not change the color
temperature of the display. Setting the color temperature to a value higher
than this results in more blue light, and setting a lower value will result in
more red light.

Default values:

  Daytime temperature: 6500K
  Night temperature: 4500K

Please report bugs to <https://github.com/jonls/redshift/issues>

Three ways to set 3000 Kelvin with redshift:

$ redshift -P -O 3000 -m drm
$ redshift -P -O 3000 -m randr
$ redshift -P -O 3000 -m vidmode

and reset the colors to normal:

$ redshift -x -m randr
$ redshift -x -m drm
$ redshift -x -m vidmode

All three should be used, just in case for example xgamma was used which did its changes in vidmode and until you reset it in vidmode too, you'll still see some color tints.

Or, if you were interested in setting the gamma values to less red (but first reset everything with the above 3 redshift lines):

$ redshift -P -O 6500k -g 0.8:1:1
Using method `randr'.

(for some reason color temperature must be specified or else you can't use -g to set the gamma, with redshift)

On Gentoo, here are the packages that own those binaries:

Gentoo Package : executable binary  
x11-apps/xrandr: /usr/bin/xrandr  
x11-apps/xgamma: /usr/bin/xgamma  
x11-misc/redshift: /usr/bin/redshift

If you're running X as non-suid root and are interested to find out which program (its name and location) is setting or resetting your gamma/RGBcolors, there's a way to find out here.