[roman]

Usa el evento OnDrawColumnCell:

procedure TForm1.DBGrid1DrawColumnCell(
  Sender: TObject; const Rect: TRect;
  DataCol: Integer; Column: TColumn; State: TGridDrawState);
begin
  if not (gdSelected in State) then
  begin
    if Odd(Table1.RecNo) then
      DBGrid1.Canvas.Brush.Color := clYellow
    else
      DBGrid1.Canvas.Brush.Color := clGreen;
  end;

  DBGrid1.DefaultDrawColumnCell(Rect, DataCol, Column, State);
end;

Sólo reemplaza clYellow y clGreen por coores de tu agrado.

// Saludos