背景颜色

//fill column A with solid red color from hex
worksheet.Column(1).Style.Fill.PatternType = ExcelFillStyle.Solid;
worksheet.Column(1).Style.Fill.BackgroundColor.SetColor(ColorTranslator.FromHtml("#FF0000"));

//fill row 4 with striped orange background
worksheet.Row(4).Style.Fill.PatternType = ExcelFillStyle.DarkHorizontal;
worksheet.Row(4).Style.Fill.BackgroundColor.SetColor(Color.Orange);