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         Colors in the Linux VTs              ##  ##  ##  ##  ##  ##
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         by Emanuel Berg (incal)              #   ##    ##    #   ##
           moasenwood@zoho.eu                 ######  ##  ##  ######

           updated 2022-01-28               underground experts united

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[The Linux VTs = the Linux virtual terminals, sometimes
 refered to as the ttys or simply "the console".]

So let's start. The 16 colors available in the Linux VTs are
individually defined by combining data from three files.
The three files correspond to the colors red, green, and blue.
It is an implementation of the familiar additive RGB color
model. [1]

The files have the same format, they all consist of a single
line of 16 comma-separated integers ranging from 0 to 255. So,
for example, my red file looks like this:

  0,255,0,190,100,180,0,150,115,255,0,255,125,250,90,210

That means the first Linux VT color shouldn't have
any red (0), the second color should have full red (255), then
again none for the third, after that 190 for the forth - and
so on for all 16. (So 190, but how red is that? Again 255 is
the maximum so 190/255.0 ~= 0.75 or 75% red.)

By now you understand how it works. My green file looks like
this:

  0,50,155,190,100,105,180,150,115,80,185,127,125,90,255,180

Let's use color 3 as an example - the color numbers are
zero-indexed so color 3 it's the forth integer from the left.
We see it contains 190 amount of green as well.

And finally the blue file:

  0,50,0,0,255,0,180,150,115,80,0,0,255,250,255,140

So no blue for color 3. All in all, color 3 is 190 red,
190 green, and 0 blue. 190 is 'be' in hex, so if the color is
described in hexadecimal pairs of 2, i.e. using the #RRGGBB
notation, color 3 would indeed "be" #bebe00.

Now examine your own files at:

  /sys/module/vt/parameters/default_red
  /sys/module/vt/parameters/default_grn
  /sys/module/vt/parameters/default_blu

As seen, the colors names aren't mentioned in those files.
Instead they appear in a particular order specified by the
ANSI standard: [2]

  black
  red
  green
  yellow
  blue
  magenta
  cyan
  white

After these follows 8 additional colors, they are supposed to
be bright versions of the above colors in the same order.
That means if one looks on the list above but continues
further down, after white would come "bright black" - which is
sometimes put to gray - then "bright red" (pink perhaps?), and
so on.

However, as is the case with the first 8 colors, which are the
intended non-brights, you can assign _any_ RGB color to any of
the 16 colors available!

That said, to somewhat stick to the standard colors is
recommended. But no rule without exception, as always.

if you feel you don't need a bright yellow (color 11) you can
turn that into for example orange - 255-127-0 (#ff7f00) is
a good start ...

However, if you do that, be aware that in some programs one
refers to these colors by names, not number. If you redefine
bright yellow to orange, in such programs you'd set something
to orange by referring to it as yellow. Unless you can
workaround this with aliases and the like it can get
confusing. Still, should be pretty undramatic, right?

Also, sticking to the intended colors probably have another,
bigger advantage, because they are probably selected because
they are are easily recognizable/discernable by the human eye.
They will almost always work.

Here [3] are the best colors I found, so far:

     normal                         bright
     bk  r   g   y  bl   m   c   w  bk    r   g   y  bl   m   c   w
  r  0 255   0 190 100 180   0 150  115 255   0 255 125 250  90 210
  g  0  50 155 190 100 105 180 150  115  80 185 127 125  90 255 180
  b  0  50   0   0 255   0 180 150  115  80   0   0 255 250 255 140

Check out [4] for an example how to use sed(1) to set the
colors without having to insert the values into the default_*
files each time. Instead, you'd use a single file, more neatly
organized, as above, the sed script will then process it and
put the values into the RGB files.

Some extra material:

  * For ls(1) to really look good, set it up with
    a dircolors(1) script. [5]

  * On OpenBSD, use colorls(1) [6] to get terminal emulator
    colors with ls.

  * If you want the same colors as in the Linux VTs in
    X applications (e.g., xterm), note that the values above
    are decimal integers in the 0-255 range (discrete base
    10), but, in .Xresources you'd need their hex
    equivalents (base 16) to get the same value. So for
    example if you'd like green (color 2) defined as 0-85-0
    in the VTs in X you'd get the hex value of 85

      $ echo "obase=16; 85" | bc
      55

    and in ~/.Xresources, where the color order is the same,
    put:

      xterm*color2: #005500

    Here are some zsh functions to convert between bases [7]
    even more easily than the bc example.

GLHF! :)


[1] https://en.wikipedia.org/wiki/RGB_color_model

[2] https://en.wikipedia.org/wiki/ANSI_escape_code

[3] https://dataswamp.org/~incal/cols/color_sets/normal.txt

[4] https://dataswamp.org/~incal/cols/run

[5] https://dataswamp.org/~incal/scripts/cols

[6] https://undeadly.org/cgi?action=article&sid=20110225013806&mode=expanded

[7] https://dataswamp.org/~incal/conf/.zsh/math

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