Nested decorators methods

I'm now studying the decorator pattern, here some example code (PHP) :

abstract class component{

  public function drawShape(){};

}

class concreteComponent extends component{

   public function drawShape(){//code};

}

class decoratorComponent extends component{

  private $component;

  public function __construct($component){ $this->component=$component; }

  public function drawShape(){

      $this->component->drawShape();

  }

}

class borderDecorator extends decoratorComponent{

  public function drawShape(){

    $this->drawBorder();
    $this->component->drawShape();

  }

  public function setBorder(){};
  public function drawBorder(){};

}

class bgColorDecorator extends decoratorComponent{

  public function drawShape(){

    $this->drawBgColor();
    $this->component->drawShape();

  }

  public function setbgColor(){};
  public function drawBgColor(){};

}

Ok, now:

$test=new concreteComponent();
$border=new borderDecorator($test);
$border->setBorder(10);
$bgColor= new bgColorDecorator($border);
$bgColor->setBgColor(#000);

Now I have a component decorated with a #000 bg color and a 10(some unit) border.

With

$bgColor->drawShape(); 

it means drawBgColor + drawBorder + drawShape and all right, BUT:

How can I modify or remove the border??

$bgColor-> ???

The bgColor class can't access directly the border methods...

Thanks