How to Choose Colors for Your CLI Applications

Summary

Let’s say you’re creating a CLI tool which has to display syntax highlighted source code. You begin by choosing some colors which look nice with your chosen terminal theme:~ — zsh — Sorcerer — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █Nice! However, who knows if it’ll still look good for people who use a theme different to yours? It seems sensible to try out the defaults, at least. Let’s start with the macOS Terminal.app default theme:~ — zsh — Basic — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █~ — zsh — Basic — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █Youch! It seems fair to try the Tango themes next, since those are the default on e.g. Ubuntu:~ — zsh — Tango Light — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █~ — zsh — Tango Dark — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █Hmm, better, but not by much. Finally, let’s try what is likely the most popular custom terminal theme – Solarized:~ — zsh — Solarized Light — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █~ — zsh — Solarized Dark — 51×11% highlight foo # just some docs func HelloWorld() [12]u8 { return "hello world\n" } Finished highlighting in 0.02 seconds. % █Well then … Let’s take a look at each palette and investigate.Sorcerer~ — zsh — Sorcerer — 51×11% colortest ██ black ██ brblack ██ red ██ brred ██ green ██ brgreen ██ yellow ██ bryellow ██ blue ██ brblue ██ magenta ██ brmagenta ██ cyan ██ brcyan ██ white ██ brwhite % █In Sorcerer, all colors are readable on the default backgr...