Returns the HTML-style hex code for the Colour.

        Returns:
            str: the colour as a HTML-sytle hex string

def hex(self):
        """
        Returns the HTML-style hex code for the Colour.

        Returns:
            str: the colour as a HTML-sytle hex string
        """
        return "#{:02x}{:02x}{:02x}".format(self._r, self._g, self._b).upper()