Looping on materials..

I am trying to loop on every materials to change the color but I only arrive to the "Starting" message and, without an error, I do not get the "array length" message. Please help. The code:

 private var r : Renderer[];
 
 function Start () {
 Debug.Log("Starting");
 r = gameObject.GetComponentsInChildren(Renderer,true);
 Debug.Log("Array lenght:" + r.Length);
   for (var m : Renderer in r) {
         m.material.color.a=0;
     }
     
 }