TreeView.Color:=$xxxxxxxx

unit Unit1;

interface

uses
  Classes, Forms, StdCtrls, Controls, ComCtrls, SysUtils;

type
  TForm1 = class(TForm)
    TreeView1: TTreeView;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure Button2Click(Sender: TObject);

  private

  public

  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  i: Integer;
  p: Pointer;

begin
  TreeView1.Items.BeginUpdate;
  Application.ProcessMessages;
  for i:= 0  to  300 - 1  do
  begin
    new(p);
    TreeView1.Items.AddChildObject(nil,FloatToStr(random* 100 ),p);
  end;
  TreeView1.Items.EndUpdate;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  Randomize;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  TreeView1.Color:=$FFFFFF;
  TreeView1.Color:=$00FFFF;
end;

end.