public class Model2
    {
        public List<MItem2> Items { get; set; }
    }

    public class MItem2
    {
        public Color FillColor { get; set; }
        public string Text1 { get; set; }
        public List<MItem2> Items { get; set; }

        public MItem2(string text1, Color fillColor)
        {
            Text1 = text1;
            FillColor = fillColor;
        }
    }

    public partial class MainWindow2 : Window
    {
        private Model2 model;
        public MainWindow2()
        {
            InitializeComponent();

            model = new Model2();
            model.Items = new List<MItem2>()
            {
                new MItem2("Item 1",Colors.Red)
                {
                    Items = new List<MItem2>()
                    {
                        new MItem2("Item 11",Colors.Red)
                        {
                            Items = new List<MItem2>()
                            {
                                new MItem2("Item 111",Colors.RoyalBlue)
                                ,
                                new MItem2("Item 112",Colors.DarkBlue)
                            }
                        }
                        ,
                        new MItem2("Item 12",Colors.SandyBrown)
                    }
                }
                ,
                new MItem2("Item 2",Colors.RosyBrown)

            };
            this.DataContext = model;
        }
    }