* Get the background fill color.
*
* @return fill color, null if color is not set
*/
public XSSFColor getFillBackgroundColor() {
CTPatternFill ptrn = _fill.getPatternFill();
if (ptrn == null) return null;
CTColor ctColor = ptrn.getBgColor();
return ctColor == null ? null : new XSSFColor(ctColor);
}