问Delphi颜料盒在颜色改变后出现故障

EN

procedure TForm1.PBPaint(Sender: TObject);
var
  Bean: TBean;
begin
  PB.Color := $008800;
  Bean := Snake.Head;
  while not (Bean = Snake.Tail) do
  begin
    PB.Canvas.FillRect(TRect.Create(Bean.x * 30, Bean.y * 30, Bean.x * 30 + 30, Bean.y * 30 + 30));
    Bean := Bean.Next;
  end;
  PB.Canvas.FillRect(TRect.Create(Bean.x * 30, Bean.y * 30, Bean.x * 30 + 30, Bean.y * 30 + 30));
  //PB.Color := $000055;
  PB.Canvas.FillRect(TRect.Create(Fruit.x * 30, Fruit.y * 30,Fruit.x * 30 + 30,Fruit.y * 30 + 30));
end;