Workbook workbook = new Workbook();
//Set version to Version2007 or above Version
workbook.Version = ExcelVersion.Version2007;
Worksheet sheet = workbook.Worksheets[0];
CellRange cell = sheet.Range["A1"];
cell.Style.Color = (Color.FromArgb(87, 37, 125));
workbook.SaveToFile("result.xlsx",ExcelVersion.Version2007);