unit Unit1;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;
type
  TForm1 = class(TForm)
    CheckBox1: TCheckBox;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

end.

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    CheckBox1: TCheckBox;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    { Private declarations }
    OldCheckBox:TCheckBox;
  public
    { Public declarations }
  end;

  TMyCheckBox = class(TCustomCheckBox)
  private
    function GetMyColor:TColor;
    procedure SetMyColor(value:TColor);
  public
    procedure MyMetod;
    property MyColor:TColor read GetMyColor write SetMyColor;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

var
  FColor:TColor;
  MyCheckBox:TMyCheckBox;

function TMyCheckBox.GetMyColor:TColor;
begin
Result:=FColor;
end;

procedure TMyCheckBox.SetMyColor(value:TColor);
begin
FColor:=value;
end;

procedure TMyCheckBox.MyMetod;
begin
MessageBox(0, 'Ok', '', MB_OK);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
MyCheckBox.MyMetod;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
MyCheckBox.Checked:=True;
MyCheckBox.MyColor:=clYellow;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
MyCheckBox:=TMyCheckBox(CheckBox1);
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
Color:=MyCheckBox.MyColor;
end;

end.