HSSFWorkbook workbook = new HSSFWorkbook();
HSSFCellStyle style = workbook.createCellStyle();
style.setFillForegroundColor(HSSFColor.LIME.index);
style.setFillBackgroundColor(HSSFColor.GREEN.index);
style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND); // 要有这一句