oh-my-zsh/lib/spectrum.zsh

# A script to make using 256 colors in zsh less painful.
# P.C. Shyamshankar <sykora@lucentbeing.com>
# Copied from https://github.com/sykora/etc/blob/master/zsh/functions/spectrum/

typeset -AHg FX FG BG

FX=(
  reset     "%{%}"
  bold      "%{%}" no-bold      "%{%}"
  dim       "%{%}" no-dim       "%{%}"
  italic    "%{%}" no-italic    "%{%}"
  underline "%{%}" no-underline "%{%}"
  blink     "%{%}" no-blink     "%{%}"
  reverse   "%{%}" no-reverse   "%{%}"
)

# Build the tables with array operations instead of a 256-iteration loop
() {
  setopt localoptions noksharrays
  local -a codes fg bg
  codes=({000..255})
  fg=( "%{"$'\e'"[38;5;"${^codes}"m%}" )
  bg=( "%{"$'\e'"[48;5;"${^codes}"m%}" )
  FG=( ${codes:^fg} )
  BG=( ${codes:^bg} )
}

# Show all 256 colors with color number
function spectrum_ls() {
  setopt localoptions nopromptsubst
  local ZSH_SPECTRUM_TEXT=${ZSH_SPECTRUM_TEXT:-Arma virumque cano Troiae qui primus ab oris}
  for code in {000..255}; do
    print -P -- "$code: ${FG[$code]}${ZSH_SPECTRUM_TEXT}%{$reset_color%}"
  done
}

# Show all 256 colors where the background is set to specific color
function spectrum_bls() {
  setopt localoptions nopromptsubst
  local ZSH_SPECTRUM_TEXT=${ZSH_SPECTRUM_TEXT:-Arma virumque cano Troiae qui primus ab oris}
  for code in {000..255}; do
    print -P -- "$code: ${BG[$code]}${ZSH_SPECTRUM_TEXT}%{$reset_color%}"
  done
}