var workbook = new XLWorkbook();
var ws = workbook.Worksheets.Add("Multiple Ranges");

// using multiple string range definitions
ws.Ranges("A1:B2,C3:D4,E5:F6").Style.Fill.BackgroundColor = XLColor.Red;

// using a single string separated by commas
ws.Ranges("A5:B6,E1:F2").Style.Fill.BackgroundColor = XLColor.Orange;

workbook.SaveAs("MultipleRanges.xlsx");