# File lib/sass/script/functions.rb, line 891
    def change_color(color, kwargs)
      assert_type color, :Color
      with = Sass::Util.map_hash(%w[red green blue hue saturation lightness alpha]) do |name, max|
        next unless val = kwargs.delete(name)
        assert_type val, :Number, name
        [name.to_sym, val.value]
      end

      unless kwargs.empty?
        name, val = kwargs.to_a.first
        raise ArgumentError.new("Unknown argument $#{name} (#{val})")
      end

      color.with(with)
    end