256 Color Palette Numbers

colortest.sh

#!/bin/bash

# System Colors
for line in {0..7}; do
	for col in {0..1}; do
		code=$(( $col * 8 + $line ))
		printf $'\e[38;05;%dm %03d' $code $code
	done
	echo
done

echo

# Color Cubes (6x6x6)
for line in {16..51}; do
	for col in {0..5}; do
		code=$(( $col * 36 + $line ))
		printf $'\e[38;05;%dm %03d' $code $code
	done
	echo
done

echo

# Grayscale Ramp
for code in {232..255}; do
	printf $'\e[38;05;%dm %03d' $code $code
	echo
done