print 256 colors in terminal

color.sh

#!/bin/bash

effs=(0 1 2 7 9)
effs2=(0 1 2 3 4 5 6 8)

for eff in "${effs[@]}" ; do
  for i in {30..37} ; do
    for j in {40..47} ; do
      ansi_eff="${eff};${i};${j}m"
      printf "\033[${ansi_eff} ${ansi_eff} \033[0m"
    done
    printf "\n"
  done
  printf "\n"
done

for eff in "${effs2[@]}" ; do
  ansi_eff="${eff};37;40m"
  printf "\033[${ansi_eff} ${ansi_eff} \033[0m"
done
printf "\n"

printf "\n"

for i in {0..255} ; do
  printf "\x1b[38;5;%sm%5d\e[0m" "$i" "$i"
  if (( ($i) %16 == 15 )); then
    printf "\n";
  fi
done

printf "\n"

for i in {0..255} ; do
  printf "\x1b[48;5;%sm%4d \e[0m" "$i" "$i"
  if (( (i) % 16 == 15 )); then
    printf "\n";
  fi
done