A.   Enter the following code in the TDBGrid's OnDrawDataCell event:

Procedure TForm1.DBGrid1DrawDataCell(Sender: TObject; const Rect: TRect;
  Field: TField; State: TGridDrawState);
begin
  If gdFocused in State then
    with (Sender as TDBGrid).Canvas do begin
      Brush.Color := clRed;
      FillRect(Rect);
      TextOut(Rect.Left, Rect.Top, Field.AsString);
    end;
end;

     Set the Default drawing to true.  With this, it only has to draw the highlighted cell.  If you set DefaultDrawing to false, you must draw all the cells yourself with the canvas properties.