title: CellStyle is applied only upon editing cell
body: <p>I am using this sample to change the color of a particular cell in the file</p>
  
  <pre><code>InputStream inp = new FileInputStream("C:\\temp\\vineet.xlsx");
  //InputStream inp = new FileInputStream("workbook.xlsx");
  
  
  Workbook wb = WorkbookFactory.create(inp);
  Sheet sheet = wb.getSheetAt(0);
  
  XSSFCellStyle style = (XSSFCellStyle) wb.createCellStyle();
  
  XSSFCellStyle defaultStyle = (XSSFCellStyle) wb.getCellStyleAt((short) 0);
  
  style.setFillBackgroundColor(IndexedColors.YELLOW.getIndex());
  //style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
  
  Row row = sheet.getRow(2);
  Cell cell = row.getCell(3);
  if (cell == null)
    cell = row.createCell(3);
  cell.setCellType(CellType.STRING);
  cell.setCellValue("a test");
  
  if (cell.getCellStyle().equals(defaultStyle)) {
    cell.setCellStyle(style);
  }
  // Write the output to a file
  FileOutputStream fileOut = new FileOutputStream("C:\\temp\\vineet.xlsx");
  wb.write(fileOut);
  fileOut.close();
  </code></pre>
  
  <p>at the first glance there are no changes, but when i try to edit the cell value using excel then the cell became yellow-backgrounded.</p>