There are some other tools (redshift, scr) that I'm taking a look at, the post here may not be the best solution (still very bright whites) but it's better than nothing ;)


In another post I showed how to control your monitor brightness and how to create some simple shortcuts, all this by using xrandr that is installed by default on most distributions.
This time I’m showing how to control your output’s gamma, especially how to lower the blue lights.

This doesn’t modify the monitor bachlight/gamma values but instead it works on a specific output (HDMI, DVI, DP, etc.). Therefore it works on any device and with every monitor.

We saw that brightness can be easily modifying by typing*:

xrandr --output DVI-I-1 --brightness 0.7

*to check your connected output(s) simply run xrandr

To control gamma type:

xrandr --output DVI-I-1 --gamma 1:1:1
same as
xrandr --output DVI-I-1 --gamma 0:0:0

These are the default gamma values for Red, Green and Blu lights (RGB). Now you can lower them and see how it changes, you may also want to include brightness to control all in a single command.

xrandr --output DVI-I-1 --gamma 1:0.7:0.5 --brightness 0.6
same as
xrandr --output DVI-I-1 --gamma 1:.7:.5 --brightness 0.6

In this case I lowered by half the blue lights and by a third (roughly) the greens.

So remember, these 3 values are R:G:B, a color is turned off when set to 0.01

Try this out:

xrandr --output DVI-I-1 --gamma 5:.01:.01 --brightness 0.6


If you didn’t know lights mix together as additive colors, whereby white light is the result of the mix and therefore it contains the entire colors spectrum.
Contrarily subtractive colors create black (or dark brown) when the primary colors red (magenta), blue (cyan) and yellow are mixed together, you can see this if you mix paint or pigments for example.
The color of an object tells you what colors in the visual spectrum are reflected and what aren’t.
I.e. a tomato reflects red light but absorbs every other colors, a white object reflects all the visible spectrum (as I said white contains all colors) and a black object absorbs all the colors (you can “see” this by walking around at night, sure not many colors are there to see).