ruby-256-color.rb

(0..15).each do |i|
  print "\e[38;5;#{i}m#{"%3d" % i}\u2588 "
  puts "" if i % 8 == 7
end
puts ""

(16..231).each do |i|
  print "\e[38;5;#{i}m#{"%3d" % i}\u2588 "
  puts "" if (i - 16) % 6 == 5
end
puts ""

(232..255).each do |i|
  print "\e[38;5;#{i}m#{"%3d" % i}\u2588 "
  puts "" if (i - 232) % 12 == 11
end

ruby-true-color.rb

(0..15).each do |r|
  (0..7).each do |g|
    (0..7).each do |b|
      print "\e[38;2;#{r*16};#{g*32};#{b*32}m\u2588"
    end
  end
  puts ""
end