How to set properties for dynamic text ?

Hi. I have dynamic textboxes which is included in the movieclip button. I set the text like this :  " buttona.label_txt.text" . However when the button was hit, the color of the button changed based on what I've set but the text is missing. I already check the properties of the textbox and already make sure the color was black, as it was supposed to be. But it still missing.

Here is the code:

var _list:Array = ["XXXquestionsXXX"];

var _marks:Array = [];

var i:int;

var myscore = 0;

question_txt.text = _list[0];

buttonA.label_txt.text = "A. Chicken";

buttonA.addEventListener(MouseEvent.CLICK, q1);

function q1(event:MouseEvent):void

{

  if(event.currentTarget == buttonA)

  {

  _marks.push("Jawapan anda : A. chicken /" + "Correct");

  var SelColor1:Number = 0XFFFF0;

  var myColorTransform1 = new ColorTransform();

  myColorTransform1.color = SelColor1;

  buttonA.transform.colorTransform = myColorTransform1;

  }