Overview:

• tcolors - get / set terminal ANSI colors (palette, foreground, background, cursor)
• tcolors-gtk - simple GTK interface for tcolors
• tcolorsinfo - test terminal ANSI colors
• tcolorsinfo8 - tcolorsinfo wrapper for quick test of base 8 colors

Acknowledgements:

• code for retrieving terminal colors was adopted from http://xyne.archlinux.ca/projects/python3-colorsysplus/

There are 5 modes of operation (see below):

$ tcolors --help
usage: tcolors [-h] {p,f,b,c,x} ...

Get/Set terminal ANSI colors.
Color can be given as name or RGB specification (e.g., #rrggbb).

positional arguments:
  {p,f,b,c,x}
    p          get/set palette color
    f          get/set foreground color
    b          get/set background color
    c          get/set cursor color
    x          get/set as/from X resources

optional arguments:
  -h, --help   show this help message and exit

For each mode bring up help by passing -h or --help, e.g.:

$ tcolors x --help
usage: tcolors x [-h] [-p] [--prefix PREFIX] [file]

Get/Set colors as/from X resources.

positional arguments:
  file             X resources source file; '-' for stdin

optional arguments:
  -h, --help       show this help message and exit
  -p, --print      don't apply, print-out only
  --prefix PREFIX  X resources prefix (default: *)

Examples:

# get palette color 1
$ tcolors p 1
#9d2d2d

# set palette color 1 to red
$ tcolors p 1 red

# set foreground color to gray90
$ tcolors f gray90

# set background color to gray10
$ tcolors b gray10

# set cursor color to '#FF5500'
$ tcolors c '#FF5500'

# get foreground, background, cursor and 0-15 palette colors in X resources format
$ tcolors x
*.foreground: #e5e5e5
*.background: #1a1a1a
*.cursorColor: #ff5500
*.color0: #050505
*.color1: #ff0000
*.color2: #45a345
*.color3: #db9c2e
*.color4: #384580
*.color5: #a43fa4
*.color6: #229f9f
*.color7: #aeaeae
*.color8: #4d4d4d
*.color9: #c04f4f
*.color10: #70c066
*.color11: #d4c668
*.color12: #606cb5
*.color13: #be63be
*.color14: #68bbbb
*.color15: #dddddd

# set colors from X resources
$ tcolors x ~/.Xresources

# set colors from X resources targetted for URxvt
$ tcolors x --prefix 'URxvt*' ~/.Xresources

$ tcolors-gtk --help
usage: tcolors-gtk [-h] [--prefix PREFIX] [file]

Set terminal ANSI colors.
Colors are initialized from terminal itself (if supported).
If <file> is passed, matching X resources are used instead.

positional arguments:
  file             X resources source file; '-' for stdin

optional arguments:
  -h, --help       show this help message and exit
  --prefix PREFIX  X resources prefix (default: *)

$ tcolorsinfo --help
usage: tcolorsinfo [-h] [-b] [-f] [-s] [-u] [-l] [-r] [-t]
                   [fg_range] [bg_range]

Performs simple test of terminal ANSI colors.
Uses following SGR escape sequences:

* colors 0-7   : CSI 3x/4x m
* colors 8-15  : CSI 9x/10x m
* colors 16+   : CSI 38;5;x/48;5;x m

By default it prints 0-15 foreground on 0-15 background colors split
in 2 tables. Default foreground and background colors are always included.
Output can be inverted by using '-t' option.

If at least one positional argument is specified it will determine
the output. One can specify foreground and background color ranges as
2 positional arguments. Format of each range argument is:

<start_color_index>[,end_color_index,[step]]

E.g.,

* 0,64,8        - yields: 0, 8, 16, 24, 32, 40, 48, 56
* 5,10          - yields: 5, 6, 7, 8, 9
* 35            - yields: 35, 36, 37, 38, 39, 40, 41, 42

Examples:

$ tcolorsinfo 0,16       - 0-15 foreground colors on 0-7 backgrounds
$ tcolorsinfo 0,16 0,16  - 16x16 color cube

positional arguments:
  fg_range
  bg_range

optional arguments:
  -h, --help        show this help message and exit
  -b, --bold        CSI 1 m
  -f, --faint       CSI 2 m
  -s, --standout    CSI 3 m
  -u, --underlined  CSI 4 m
  -l, --blink       CSI 5 m
  -r, --reverse     CSI 7 m
  -t, --transpose

X resources are normally preprocessed with preprocessor (e.g., cpp) and that makes it easy to separate terminal schemes into separate files. I put color schemes into ~/.xcolors directory and reference the default one in ~/.Xresources file in the following way:

! xcolors --------------------------------------------------------------------
#include ".xcolors/default"

With the help of tcolors it's easy to implement simple color scheme switcher / selector. That's handy for switching between couple of favorite schemes, or trying out new schemes.

To serve this purpose I've created myself simple bash script called tcolors-sel (source). It is built on top of scroller (source) which is separate program providing simple VI like scrolling over its arguments.