Hi rainkuan9,
We have created a sample to achieve your requirement. Please refer to the below code example and sample.
Code example:
[C#]
//setting the visual type
paletteGroupBar1.VisualStyle = Syncfusion.Windows.Forms.VisualStyle.OfficeXP;
//Creating SymbolPalette
Syncfusion.Windows.Forms.Diagram.Rectangle rect = new Syncfusion.Windows.Forms.Diagram.Rectangle(100, 100, 100, 50);
SymbolPalette sym = new SymbolPalette();
sym.Name = "Symbol";
sym.AppendChild(rect);
paletteGroupBar1.AddPalette(sym);
//background color for GroupBarItem
paletteGroupBar1.GroupBarItems[0].Client.BackColor = Color.Wheat;
Sample:
Sample
Regards,
Naganathan K G