def theme_color(self):
        """
        A member of :ref:`MsoThemeColorIndex` or |None| if no theme color is
        specified. When :attr:`type` is `MSO_COLOR_TYPE.THEME`, the value of
        this property will always be a member of :ref:`MsoThemeColorIndex`.
        When :attr:`type` has any other value, the value of this property is
        |None|.

        Assigning a member of :ref:`MsoThemeColorIndex` causes :attr:`type`
        to become `MSO_COLOR_TYPE.THEME`. Any existing RGB value is retained
        but ignored by Word. Assigning |None| causes any color specification
        to be removed such that the effective color is inherited from the
        style hierarchy.
        """
        color = self._color
        if color is None or color.themeColor is None:
            return None
        return color.themeColor