Problem with setFillBackgroundColor in HSSF

[Neeraj Dhiman]

hi friends, i am trying to create a excel using POI 3.5.
Every thing is working fine but background color is not reflected in excel.
Code:

      SSFWorkbook workbook = new HSSFWorkbook();
      HSSFSheet sheet =workbook.createSheet("Excel Sheet");
      HSSFRow rowhead =sheet.createRow((short) 0);
      rowhead.createCell((short)0).setCellValue("My Test Report ");
      HSSFCellStyle cellstyle = workbook.createCellStyle();
      cellstyle.setFillBackgroundColor(HSSFColor.GREEN.index);
      cellstyle.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
      cellstyle.setAlignment(HSSFCellStyle.ALIGN_CENTER);
      HSSFCell cell  = rowhead.getCell(0);
      cell.setCellStyle(cellstyle);

Although alignment works fine. and i found the target color of cell is black not Green.

Any help, Thanks in Advance.