How to choose colors for your CLI applications (2023)

[layer8]

As long as CLI programs stick to the 8 or 16 standard colors and refrain from setting background colors (inverse mode is fine), as well as from explicitly setting white or black as text color, everyone can reasonably configure their terminal colors so that everything is readable.

When going beyond that, the colors really need to be configurable on the application.

[JohnLeitch]

> refrain from setting background colors

That's the thing though, setting bg color opens up a lot of options, and constraining to invert is not sufficient in my opinion.

[Arch-TK]

Configurable within the application... at runtime.

I want to be able to switch existing terminals with existing applications between themes.

[j4cobgarby]

Use only default (white/black), red for bad, green for good. If you need more than that, like vim or whatever, then maybe a 'fullscreen' TUI is better, with a specified background and foreground. For CLI tools, I'm not sure if I prefer more colours.

The CSS to make the terminals look like iTerm was smooth, to the point I read them as screenshots.

[BeetleB]

Hard disagree on the red/green. Use whatever you think appropriate and make it user configurable.

[busterarm]

> red for bad, green for good

8% of men of Northern European descent (and 0.4% of women) are red-green colorblind. That'd be a terrible choice. Use blue-orange, blue-red, or purple-green.

[fassssst]

Color is cultural. Red is associated with good in China

[red_admiral]

Eh, LS_COLORS is sometimes useful once the meanings are in your subconscious.

[tolciho]

A confused user once stopped by, they had a blank terminal, so I showed them how to select all which revealed the helpfully black on black text. These days I compile colour support out of st, or set *colorMode:false for xterm. "But you can customize the colours" is a typical response, to which one might respond that one has grown weary of pushing that particular rock, and moreover one may be busy with other things at a drag-out monitor in a server room at three in the morning that has helpfully dark blue text on a black console, or worse if some high-minded expert has gone and rubbed the backside of a unicorn everywhere so that they may improve the "legibility".

[s_dev]

Colourful terminals are so useful. I have mine colour coded according to the working directory depending on the project. So I can see which terminal is associated with which project even if there are twenty terminals open. The scripts are even in my servers so when I ssh in to them it changes colour as well.

https://michael.mior.ca/blog/coloured-ssh-terminals/

[kiddico]

Very cool. Thanks for sharing!

[red_admiral]

There's an ever more basic rule: don't just make your text white (ANSI 37m) because you assume the terminal will have a dark background. Even white-on-black (37;40m), while usually readable, can stand out the wrong way if you assume that everyone is using dark mode.

[account42]

IMO if your terminal theme does not provide high contrast for "white" text on the default or "black" backgrounds, that's for you to fix. If you want a light terminal then change the color scheme to map "black" to a bright color and "white" to a dark color while making sure that other colors have good contrast to your "black". Don't just change the default foreground and background color and expect every single color using program to fix your mess.

[ori_b]

As long as you respect the NO_COLOR variable, it will work for me.

https://no-color.org/

[wredcoll]

That's a funny example. I have no issues with the idea of course but in my day to day life I'm way more likely to encounter an issue with colors being lost after sent to a pager or a log file or tee or what not

[jammcq]

I'm a bit color blind and it might be quite common to show errors in red but when the background is black, I can't see it at all.

[bradrn]

Neither can I. Luckily tweaking the colours can make it somewhat readable. (Sometimes…)

[joshka]

I made the "Aardvark Blue" a while back[1] to solve some of the problems that most color schemes have. The goal of this theme is that:

- colors are fairly natural

- background and black are distinct

- grays are naturally ordered avoiding full black

- light and dark colors are distinct from each other

- all colors look good on background, black, dark gray, gray, white

We use this for all the screenshots on https://ratatui.rs and https://github.com/ratatui/ratatui

It's available from the usual places https://iterm2colorschemes.com/, https://windowsterminalthemes.dev/?theme=Aardvark%20Blue, built in to ghostty, extension for vscode etc.

[1]: https://github.com/mbadolato/iTerm2-Color-Schemes/pull/417

[tasuki]

Funny thing, those are not "the usual places" I've ever heard of, and I care somewhat about color schemes. Each of us lives in our own bubble... (my bubble is not iterm2 and not windows)

[anal_reactor]

The problem with CLI colors is that they operate on the wrong abstraction layer. Individual program shouldn't send "this text is red" but "this text signals failure" and then terminal interprets "failure" as "red". Until this change happens (never) colors in CLI will remain a hot mess.

[makapuf]

I really think we should converge to semantic codes. By example Background is zero, standard is 7, positive / negative, highlight, colored1,2,3 .. with correct defaults, and let the user have a common 8 or 16 colors palette in the terminal for all textmode apps. Imagine having some kind of unified color themes in the terminal.

[nateroling]

I’ve bounced off of LazyGit multiple times because I never figured out how to make it play nice with a light theme terminal.

I haven’t used dark mode anything for years. I set my monitor so it’s roughly as bright, or slightly brighter than, a piece of white paper.

No more flash-bangs when some website doesn’t support dark mode.

[xenophonf]

I really wish you wouldn't. All the rinky dink colors and animations screw with the CLI output when you don't correctly detect whether the user's running the app interactively.

Keep it plain text. Regular, old, boring output is good.

[skydhash]

I dislike when devs only try to detect if it’s a tty, then enable all their gimmicks without even providing a flag. Not everything is xterm-256color.

[bitwize]

I agree. So many TUIs from webshit devs don't even bother to call isatty, let alone check terminfo to see if ANSI escape codes are even valid for this terminal.

But modern open source subscribes to Mao's Continuous Revolution Theory. Calls for some measure of stability and sanity are usually dismissed with some form of the argument "awwww, is poor diddums afwaid of a widdle change?" Or in this case, "still using vi on your ADM3A, old timer? Our software is not for you."

[davidw]

Yeah. "The only winning move is not to play".

[bl4kers]

Big blocks of text are difficult to parse

[alias_neo]

I recently spent several evenings re-working all of my colours across all of my computers and screens; terminals, IDEs, etc. Ultimately, despite using the same tools, and always dark mode, across all of my machines, the setup for each was different.

I think it's safe to set a standard colour-set so that it's immediately usable, but beyond that, a user should be customising to their requirements.

Perception differs among people; many of the colours OP listed as unreadable, were barely an issue, bright yellow being the only one I could unequivocally agree on. Perhaps display type, configuration and colour calibration is an important factor, as well as individual perception, ambient conditions, brightness levels, contrast, and perhaps even more variables have a significant effect.

I've also learned, since adding an OLED Monitor to my desk alongside the IPS ones, that it's possible to have too much contrast; brightly coloured text alongside pixels that are literally off can be just as problematic to read at times, as low-contrast.

[jph]

If you want a quick easy way to add some colors to your own shell scripts:

    export STDOUT_COLOR_START=''
    export STDOUT_COLOR_STOP=''
    export STDERR_COLOR_START=''
    export STDERR_COLOR_STOP=''

In your shell script:

    print_stdout() {
        printf %s%s%s\\n "${STDOUT_COLOR_START:-}" "$*" "${STDOUT_COLOR_STOP:-}"
    }

    print_stderr() {
        >&2 printf %s%s%s\\n "${STDERR_COLOR_START:-}" "$*" "${STDERR_COLOR_STOP:-}"
    }

Source: https://github.com/sixarm/unix-shell-script-kit

The source also has functions for nocolor, and detecting a dumb terminal setup that doesn't use colors, etc.

[kps]

1. That script's color check doesn't check that the output is a terminal. Also test

    tty -s

2. Don't hardcode escape sequences. Use (e.g.)

    export STDOUT_COLOR_START="`tput setaf 4`".

[wpm]

If you're writing a zsh script and not worried about portability, you can also use the prompt expansion colors with "print".

    print_color () {
      print -P "%F{$1}$2%f"
    }

And then to use it

   print_color "green" "This is printed in green"

[godelski]

That seems needlessly cumbersome, why not

  declare STDOUT_COLOR='\e[34m'
  declare STDERR_COLOR='\e[31m'
  declare COLOR_STOP='\e[0m'

  print_stdout() {
      echo -e "${STDOUT_COLOR}${*}${COLOR_STOP}" &> /dev/stdout
  }

  print_stderrr() {
      echo -e "${STDERR_COLOR}${*}${COLOR_STOP}" &> /dev/stderr
  }

Like why are you exporting? Do you really need those in your environment?

And those print statements aren't going to work by default.

[direwolf20]

What is the purpose of making everything the same color?

[thinking_cactus]

Interesting analysis, but perhaps it warrants a different conclusion: it's almost impossible to please everyone in this case. The resulting colours seem of some utility, but if you intend to make something more interesting you're probably annoy some (potentially large) group, in the case of legacy terminal coloring.

[hnsmhthrow]

I used solarized since it came out but I dropped it some years back. I don’t think I can use it for dark mode. It’s too washed out and dull compared to light mode which is what I used to use it with. I just use whatever VS Code or VIM gives me as a dark mode and it’s usually better.

[loicd]

In addition to $TERM, I wish there was a standard variable defined by terminal emulators that would contain the background color. This would let programs choose their colors accordingly, rather than try for a one-size-fits-all.

[0x457]

Use 8 or 16 standard colors, let me configure them via terminal emulator or give me a way to completely change color scheme. That is it. Very rarely I need per-application colors in terminal (or anywhere really).

[assimpleaspossi]

Black on white has seemed to work for centuries without issue. For general reading, throw in bold and italic and you're pretty much set. For programming, black on white is still a go to color (or lack thereof).

[seanwilson]

If the goal of the post is to pick terminal colors that contrast on both white/light and black/dark backgrounds, it means you're stuck with midtone colors (between light and dark). This is really limiting for color choice (there's no such thing as "dark yellow" for example), and lowers the maximum contrast you can have for text because you get the best contrast when one color is dark and the other is light.

Ideally, instead of the CLI app switching to "bright green", it would pick a "bright contrasting green". So if the terminal background was dark, it would pick bright green, and for light background it would pick a darker green. There isn't CLI app implementations for this? This is similar to how you'd implement dark mode in a web app.

[account42]

> Ideally, instead of the CLI app switching to "bright green", it would pick a "bright contrasting green". So if the terminal background was dark, it would pick bright green, and for light background it would pick a darker green. There isn't CLI app implementations for this? This is similar to how you'd implement dark mode in a web app.

The responsibility for this lies with the color scheme not the terminal program.

[JoshTriplett]

CLI apps can detect the background color of the terminal, and determine contrasting colors accordingly.

[alt187]

That's called `\e[0;92m`, aka the ANSI terminal espace sequence for bright green. You have 15 others, that will be displayed however the terminal's user wants. They're already available in most terminal color libraries, too.

[sroussey]

This is true for the console in dev tools as well.

Problem there is you can’t change css so at the moment the systems color preference changes thing will look bad.

Important considerations for custom formatters.

[sroussey]

Here is a screenshot for my personal example:

https://github.com/workglow-dev/workglow/blob/main/docs/deve...

Play with it here using dev tools (you can ignore the website itself): https://workglow-web.netlify.app/

Docs including útil for checking dark mode: https://github.com/workglow-dev/workglow/tree/main/packages/...

[bitwize]

It's 2026, and app developers are solely responsible for not causing eyehurt, even if their users insist on using the Hotdog Stand theme.

[munificent]

Tangential, but I really love the design of this blog.

[alfirous]

Me too. Typography and colors are great.

[pimlottc]

What is Sorcerer here?

[otabdeveloper4]

Step one: *always* assume a dark background.

[lifetimerubyist]

I use the built-in TokyoNight Day theme as my light theme in GhosTTY and I think it's almost perfect. Then I use TokyoNightMoon for dark. Works great. Hard to use anything else now.

If you're CLI application doesn't play nice with it (i haven't seen many) I don't use it.

[taswellian]

It's easier to see dark text on a light background for people with astigmatism.

[Arch-TK]

Most things work fine with black on white terminals.

If your software does something dumb when my theme switches to black on white during the day then I am just going to avoid using it...

[strogonoff]

Accommodating terminal colour schemes, however crazy to you they might be—white on black, black on white, dark brown on off-white Solarized-style, etc.—is basics of TUI design.

Personally I alternate between light on dark and dark on light (the latter sometimes together with OS-wide colour inversion feature).

[skydhash]

> People who use white themed terminals are psychopaths anyway

Dark background is hell for anyone with astigmatism. It’s fine with 80x24 (vga text mode), but for anything higher feels like light needles on the retina. With astigmatism everything that is bright and small is duplicated, which means small characters is very difficult to read.

[keepamovin]

Can you work this into an AGENTS.md ? Just so happen to be working on multiple TUI at the moment: text-based modern web browser, VPS rental console, agentic coding wrapper.

Colors, have been a perpetual nightmare.