废话不多说，直接来代码！！！
其中标红的才是重点！！！
代码中有时可以不用创建新文件, 如果报错的话可以通过创建新文件来进行操作（懒，没去找报错原因），不过原文件也会被修改。
操作之前做好备份！操作之前做好备份！操作之前做好备份！
下面是引入的包：
org.apache.poi.ss.usermodel.WorkbookFactory
org.apache.poi.ss.usermodel.Sheet
org.apache.poi.ss.usermodel.Row
org.apache.poi.ss.usermodel.Cell
org.apache.poi.ss.usermodel.CellStyle
File file = new File("E:/test.xlsx");File newFile = new File("E:/test1.xlsx");if(!newFile.exists()) {try {newFile.createNewFile();} catch (IOException e) {e.printStackTrace();}}FileInputStream inputStream;try {inputStream = new FileInputStream(file);Workbook workbook = WorkbookFactory.create(inputStream);Sheet sheet = workbook.getSheetAt(0);//设置背景色 CellStyle cellStyle = workbook.createCellStyle();cellStyle.setFillForegroundColor(IndexedColors.RED.getIndex());cellStyle.setFillPattern(FillPatternType.SOLID_FOREGROUND); //修改单元格颜色Row row = sheet.getRow(0);Cell cell = row.getCell(1);cell.setCellStyle(cellStyle);//对修改后的Excel进行保存FileOutputStream excelFileOutPutStream = new FileOutputStream(newFile.getAbsolutePath());workbook.write(excelFileOutPutStream);excelFileOutPutStream.flush();excelFileOutPutStream.close();} catch (FileNotFoundException e) {e.printStackTrace();} catch (EncryptedDocumentException e) {e.printStackTrace();} catch (InvalidFormatException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}