def _colorize(self, content):
        """
        Args:
            content(str): Color as a string or number 0 - 255 (Default: None)

        Returns:
            :py:class:`str`: content formatted with color

        Format ``content`` with the color specified for this progress bar

        If no color is specified for this instance, the content is returned unmodified

        The color discovery within this method is caching to improve performance
        """

        if self.color is None:
            return content

        if self._color and self._color[0] == self.color:
            return self._color[1](content)

        if self.color in COLORS:
            spec = getattr(self.manager.term, self.color)
        else:
            spec = self.manager.term.color(self.color)

        self._color = (self.color, spec)
        return spec(content)