Prints ANSI colours to the console so that it is easily readable, and fits in one screen

ansi_colours.sh

#! /bin/bash
#
# ansi colours

# basic
printf '\e[1mbasic:\e[0m\n'
for code in {0..15}
do
  if [[ $(echo "$code % 8" | bc) -ge 1 ]]
  then
    # darken text
    printf '\e[30;1m\e[48;5;%dm %3d \e[0m' $code $code
  else
    printf '\e[48;5;%dm %3d \e[0m' $code $code
  fi

  if [[ $(echo "$((code + 1)) % 8" | bc) -eq 0 ]]
  then printf '\n'
  fi
done
printf '\n'

# palette
printf '\e[1mpalette:\e[0m\n'
#
# for base in {16..196..36}
# do
#   for offset in {0..35}
#   do
#     code=$(($base + $offset))
#     printf '\e[48;5;%dm %3d \e[0m' $code $code
#     if [[][ $(echo "$((offset + 1)) % 6" | bc) -eq 0 ]]
#     then printf '\n'
#     fi
#   done
# done

# palette condensed
colour_count_total=216        # 232 max code - 16 basic
palette_colour_count=36       # 36 colours in a palette
palette_column_count=3
palette_row_colour_count=108  # 36 * 3
palette_row_count=2           # ceiling of:
                              #   ($colour_count_total - $palette_row_colour_count)
                              #     divided by
                              #   ($palette_column_count * $palette_colour_count)
                              #
                              # = ceil((216 - 108) / (3 * 36)) + 1
                              # = ceil(108 / 108) + 1
                              # = ceil(0.5) + 1
                              # = 2

for palette_row in {0..1}  # $(($palette_row_count - 1))
do
  for row_offset in {0..5}
  do
    for palette_col in {0..2}  # $(($palette_column_count - 1))
    do
      base=$(echo "$palette_col * 36 + $row_offset * 6 + $palette_row * $palette_row_colour_count + 16" | bc)

      for col_offset in {0..5}
      do
        code=$(($base + $col_offset))

        # colours go up to 232
        if [[ $code -ge 232 ]]; then break; fi

        if [[ $(echo "$palette_row * $palette_col + $row_offset * $col_offset + $row_offset + $col_offset" | bc) -ge 3 ]]
        then
          # darken text
          printf '\e[30;1m\e[48;5;%dm %3d \e[0m' $code $code
        else
          printf '\e[48;5;%dm %3d \e[0m' $code $code
        fi
      done

      # separate palettes
      printf '  '
    done
    printf '\n'
  done
  printf '\n'
done

# greys
printf '\e[1mgreys:\e[0m\n'
for offset in {0..11}
do
  base=232
  code=$(($base + $offset))
  printf '\e[48;5;%dm %3d \e[0m' $code $code
done
printf '\n'
for offset in {12..23}
do
  base=232
  code=$(($base + $offset))
  printf '\e[30;1m\e[48;5;%dm %3d \e[0m' $code $code
done

printf '\n'