I have a textbox with the following (important) properties:
this.license.Multiline = true; this.license.ReadOnly = true; this.license.ScrollBars = System.Win
You can use a disabled RichTextBox and reset the color to black afterwards.
RichTextBox
RichTextBox rtb = new RichTextBox(); rtb.IsEnabled = false; rtb.Text = "something"; rtb.SelectAll(); rtb.SelectionColor = Color.Black; rtb.SelectedText = String.Empty;