destroy all same color combination of bricks

You could put something like this on all your boxes. Note it assumes that the boxes are tagged "Red" and "Green" for red and green boxes:

 #pragma strict
 
 function OnCollisionEnter(col : Collision) {
     if (col.collider.name != "Ball")
         return;
     
     var tag = gameObject.tag;
     
     var hit : RaycastHit;
     // Check the boxes above
     while(Physics.Raycast(transform.position, Vector3.up, hit)) {
         if (hit.collider.tag != tag)
             break;
         hit.collider.enabled = false;
         Destroy(hit.collider.gameObject);
     }
     // Check the boxes below
     while(Physics.Raycast(transform.position, Vector3.down, hit)) {
         if (hit.collider.tag != tag)
             break;
         hit.collider.enabled = false;
         Destroy(hit.collider.gameObject);
     }
     Destroy(gameObject);
 }

doing anything with raycast here is overkill, this should be handled in the datamodel. Store references to your boxes in a 2D array for example (as you have rows of boxes). Or create a linked list implementation in which each box has a reference to the top and bottom box.