Format Back Wall

Set the chart back wall thickness to 4, the fill color to aquamarine and the border color to orange.

Output: BackWall.xlsx

var workbook = new Workbook();
var worksheet = workbook.Worksheets[0];
            
worksheet.GetRange("J1:L1").SetValue(new[] { "Series 1", "Series 2", "Series 3" });
worksheet.GetRange("I2:I5").SetValue(new[] { "Point 1", "Point 2", "Point 3", "Point 4" });
worksheet.GetRange("J2:J5").SetValue(new[] { 2, 4, 6, 8 });
worksheet.GetRange("K2:K5").SetValue(new[] { 4, 3, 2, 1 });
worksheet.GetRange("L2:L5").SetValue(new[] { 2, 1, -1, -2 });

var chart1 = worksheet.Charts.Add<Bar3DChart>("A1");
chart1.Size.HeightInches = 2.5;
chart1.Size.WidthInches = 3.5;
chart1.DataSource = "Sheet1!$I$1:$L$5";

chart1.Walls.BackWall.Thickness = 4;
chart1.Walls.BackWall.Fill.SolidColor = Color.Aquamarine;
chart1.Walls.BackWall.Border.Color = Color.Orange;

workbook.SaveAs("BackWall.xlsx");