uses
  RichEdit;
 // Underline styles
const
  CFU_UNDERLINETHICK = 9;
  CFU_UNDERLINEWAVE = 8;
  CFU_UNDERLINEDASHDOTDOT = 7;
  CFU_UNDERLINEDASHDOT = 6;
  CFU_UNDERLINEDASH = 5;
  CFU_UNDERLINEDOTTED = 4;
  CFU_UNDERLINE = 1;
  CFU_UNDERLINENONE = 0;
 procedure RE_SetCharFormat(ARichEdit: TRichEdit; AUnderlineType: Byte; AColor: Word);
 var
  // The CHARFORMAT2 structure contains information about
 // character formatting in a rich edit control.
 Format: CHARFORMAT2;
 begin
  FillChar(Format, SizeOf(Format), 0);
  with Format do
  begin
  cbSize := SizeOf(Format);
  dwMask := CFM_UNDERLINETYPE;
  bUnderlineType := AUnderlineType or AColor;
  ARichEdit.Perform(EM_SETCHARFORMAT, SCF_SELECTION, Longint(@Format));
  end;
 end;
 // Underline the current selection with a CFU_UNDERLINEWAVE line style (color red);
procedure TForm1.Button1Click(Sender: TObject);
 begin
  RE_SetCharFormat(RichEdit1, CFU_UNDERLINEWAVE, $50);
 end;