api.cs

private void MailMerge_FieldMerged(object sender, 
  TXTextControl.DocumentServer.MailMerge.FieldMergedEventArgs e)
{
    // custom field handling
    if (e.TableCell == null)
        return;

    // if TableCell.Name has instructions, create a CellFilterInstructions object
    // and evaluate the instructions and set the table cell color
    if (e.TableCell.Name != "")
    {
        CellFilterInstructions instructions = 
          (CellFilterInstructions)JsonConvert.DeserializeObject(
            e.TableCell.Name, typeof(CellFilterInstructions));

        // retrieve the color
        Color? color = instructions.GetColor(e.MailMergeFieldAdapter.ApplicationField.Text);

        // apply the color
        if (color != null)
            e.TableCell.CellFormat.BackColor = (Color)color;
    }
}