[roamer]

Код:

...
DBGrid.Options:=DBGrid.Options+[dgRowSelected];
...
...

procedure TDlg_SysCalend.DBGrid_CDrawDataCell(Sender: TObject;
  const Rect: TRect; Field: TField; State: TGridDrawState);
begin
  with DBGrid.Canvas do
    begin
      if (gdSelected in State) then begin
         Brush.Color:=clYellow;
         Font.Color:=clBlack;
         FillRect(Rect);
         DBGrid_C.DefaultDrawDataCell(Rect, Field, State);
      end;
  end;
end;