Try this code:
private void button1_Click(object sender, System.EventArgs e)
{
DataSet ds = new DataSet();
ds.ReadXml("data1.xml");
this.gridGroupingControl1.DataSource = ds.Tables[0];
Application.DoEvents();
this.gridGroupingControl1.TableDescriptor.Columns[1].Appearance.AnyRecordFieldCell.CellType = "RichText";
this.gridGroupingControl1.TableDescriptor.Columns[1].Appearance.AnyRecordFieldCell.BackColor = Color.LightGoldenrodYellow;
}
This shows up OK for me in your sample without explicitly setting the colwidth. If you want to set the colwidth, then call another Apllication.DoEvents so all the settings get applied.
private void button1_Click(object sender, System.EventArgs e)
{
DataSet ds = new DataSet();
ds.ReadXml("data1.xml");
this.gridGroupingControl1.DataSource = ds.Tables[0];
Application.DoEvents();
this.gridGroupingControl1.TableDescriptor.Columns[1].Appearance.AnyRecordFieldCell.CellType = "RichText";
this.gridGroupingControl1.TableDescriptor.Columns[1].Appearance.AnyRecordFieldCell.BackColor = Color.LightGoldenrodYellow;
Application.DoEvents();
this.gridGroupingControl1.TableDescriptor.Columns[1].Width = 200;
}