class Sass::Script::Value::Color

def self.from_hex(hex_string, alpha = nil)
  unless hex_string =~ /^#?([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})?$/i ||
         hex_string =~ /^#?([0-9a-f])([0-9a-f])([0-9a-f])([0-9a-f])?$/i
    raise ArgumentError.new("#{hex_string.inspect} is not a valid hex color.")
  end
  red   = $1.ljust(2, $1).to_i(16)
  green = $2.ljust(2, $2).to_i(16)
  blue  = $3.ljust(2, $3).to_i(16)
  alpha = $4.ljust(2, $4).to_i(16).to_f / 0xff if $4
  hex_string = "##{hex_string}" unless hex_string[0] == ?#
  attrs = {:red => red, :green => green, :blue => blue, :representation => hex_string}
  attrs[:alpha] = alpha if alpha
  new(attrs)
end