def mode=(mode)
      modes = [_rgb, _hsb, _name, _hex]
      @mode = modes.detect { |m| m.class.to_s.match /#{mode}/i } || begin
                raise ArgumentError, "Invalid mode given"
              end
    end
def mode=(mode)
      modes = [_rgb, _hsb, _name, _hex]
      @mode = modes.detect { |m| m.class.to_s.match /#{mode}/i } || begin
                raise ArgumentError, "Invalid mode given"
              end
    end
Set output mode.