[NumLock]

Код:

type
  TForm1 = class(TForm)
    RichEdit1: TRichEdit;
    procedure FormCreate(Sender: TObject);

procedure TForm1.FormCreate(Sender: TObject);
begin
  RichEdit1.Text:='здесь текст красного цвета';
  RichEdit1.SelStart:=12;
  RichEdit1.SelLength:=8;
  RichEdit1.SelAttributes.Color:=clRed;
  RichEdit1.SelStart:=-1;
end;