output terminal palette colors as hex

colors.sh

#!/usr/bin/env bash

# Put terminal into raw mode to capture OSC responses
stty -icanon -echo min 0 time 1

# Create temp file
tmp=$(mktemp)

# Send OSC 4 queries for all 256 colors
for i in {0..255}; do
  printf "\e]4;%d;?\a" "$i"
done

# Give terminal time to respond fully (important!)
sleep 0.2

# Read everything available into the temp file
dd bs=1 of="$tmp" status=none

# Restore terminal settings
stty sane

# Parse responses
grep -ao $'\e]4;[0-9]\+;rgb:[0-9A-Fa-f/]\+\a' "$tmp" |
while IFS= read -r resp; do
  # Extract index and rgb components
  if [[ $resp =~ $'\e]4;'([0-9]+)';rgb:'([0-9A-Fa-f]+)/([0-9A-Fa-f]+)/([0-9A-Fa-f]+)$'\a' ]]; then
    idx=${BASH_REMATCH[1]}
    r=${BASH_REMATCH[2]}
    g=${BASH_REMATCH[3]}
    b=${BASH_REMATCH[4]}

    # Convert 16-bit hex to 8-bit hex
    printf "%3d  #%02X%02X%02X\n" \
      "$idx" \
      $((16#$r / 257)) \
      $((16#$g / 257)) \
      $((16#$b / 257))
  fi
done |
sort -n