//Instantiating a Workbook object
Workbook workbook = new Workbook();
//Obtaining the reference of the first worksheet
Worksheet worksheet = workbook.getWorksheets().get(0);
Style style = workbook.createStyle();
//Setting the background color to Blue
style.setBackgroundColor(Color.getBlue());
//Setting the foreground color to Red
style.setForegroundColor(Color.getRed());
//setting Background Pattern
style.setPattern(BackgroundType.DIAGONAL_STRIPE);
//New Style Flag
StyleFlag styleFlag = new StyleFlag();
//Set All Styles
styleFlag.setAll(true);
//Get first Column
Column column = worksheet.getCells().getColumns().get(0);
//Apply Style to first Column
column.applyStyle(style, styleFlag);
//Saving the Excel file
workbook.save("book1.xls");