DBGRID问题，高手请进(5分)

AQ_adkcjcx是一个ADOQUERY,Achievement是成绩字段，我下面这段是成绩小于60分的字体在网格中显示是红色，大于60分显示蓝色。
问题：为何我的的界面出现抖动，怎样消除？

procedure TFAcjdkcx.DBGrid1DrawColumnCell(Sender: TObject;
const Rect: TRect; DataCol: Integer; Column: TColumn;
State: TGridDrawState);
var
i:integer;
begin
with DBGrid1.Canvas do
begin
i:=Fdm.AQ_adkcjcx.fieldbyname('Achievement').AsInteger;
if (i<60) then
DbGrid1.Font.Color := clRed
else
DbGrid1.Font.Color := clBlue;
end;
DbGrid1.DefaultDrawColumnCell (Rect, DataCol, Column, State);
end;

procedure TFAcjdkcx.DBGrid1DrawColumnCell(Sender: TObject;
const Rect: TRect; DataCol: Integer; Column: TColumn;
State: TGridDrawState);
var
i:integer;
begin
with DBGrid1.Canvas do
begin
i:=Fdm.AQ_adkcjcx.fieldbyname('Achievement').AsInteger;
if (i<60) then
[red]Column[/red].Font.Color := clRed
else
[red]Column[/red].Font.Color := clBlue;
end;
DbGrid1.DefaultDrawColumnCell (Rect, DataCol, Column, State);
end;

DbGrid1.DefaultDrawColumnCell (Rect, DataCol, Column, State);

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接受答案了.