def pen_color=(val)
      if val.is_a?(Numeric)
        val %= 201
        _, s, l = Color.rgb_to_hsl(*pen_color)
        val = Color.hsl_to_rgb(val, s, l)
      end
      @pen_color = val
    end
def pen_color=(val)
      if val.is_a?(Numeric)
        val %= 201
        _, s, l = Color.rgb_to_hsl(*pen_color)
        val = Color.hsl_to_rgb(val, s, l)
      end
      @pen_color = val
    end
set pen color

 @param [Array<Integer>|Symbol|Integer] val color
   When color is Array<Integer>, it means [R, G, B].
   When color is Symbol, it means the color code; like :white, :black, etc...
   When color is Integer, it means hue.