ターミナルで使える色と色番号を一覧にする ref: http://qiita.com/tmd45/items/226e7c380453809bc62a

termcolor.rb

# -*- coding: utf-8 -*-

@fg = "\x1b[38;5;"
@bg = "\x1b[48;5;"
@rs = "\x1b[0m"

def color(code)
  number = '%3d' % code
  "#{@bg}#{code}m #{number}#{@rs}#{@fg}#{code}m #{number}#{@rs} "
end

256.times do |n|
  print color(n)
  print "\n" if (n + 1).modulo(8).zero?
end
print "\n"