Change Prefab Source/Change material on ALL prefabs in the scene

Hello everyone!

I really hope someone can help me:)

I have made an endless tunnel made out of different object. The player moves forward. By clicking I want to change these objects (size,material,animation,etc.) This works.

But.. Because I work with prefabs, only the prefab changes that I've clicked. Unless it's the source of the prefabs (the first tunnel).

Does anyone know how to change ALL the prefabs that are instantiated. Also when they already are in the scene? (so that the change made by clicking remains constant)

 var tunnel : Transform;
 
 private var CreateTimer = 2.0;
 private var NextCreate = 0.0;
 public static var count = 0;
 
 function Update() 
 {
     transform.Translate(Vector3.forward * (15 * Time.deltaTime));
     
     if (Time.time > CreateTimer + NextCreate)
     {
         NextCreate = Time.time;
             
         for (var i : int = 0; i < 1; i++)
         {
             count++;
             Instantiate(tunnel, new Vector3(72.5, 26.5,count * 150), Quaternion.Euler(0, 0, 180));
         }    
     }
 }
 
 public var TargetPlane : GameObject;
 
 function OnMouseDrag ()
 {
     TargetPlane.renderer.sharedMaterial.color -= Color(0.1, 0, 0) * Time.deltaTime;
 }