XY colour value: [float, float] or None
        :rtype: list float

def color_xy(self):
        """
        XY colour value: [float, float] or None
        :rtype: list float
        """
        color_x = self._last_reading.get('color_x')
        color_y = self._last_reading.get('color_y')
        if color_x is not None and color_y is not None:
            return [float(color_x), float(color_y)]
        return None