Cannot change Materials of certain objects

Hey so basically what I have here, is when a Raycast hits any object with the script "ThePaintableDummyScript" attached to it, that object will change colors. And it cycles through each objects multiple materials to make sure it affects every material. My problem is that some objects just wont be affected at all and I have no idea why. I've compared the objects that work, to the ones that don't, and they are nearly identical besides having different shaped and sized meshes. Some of these objects also have more Materials than others. But they all basically have the same components as well, Mesh Filter, Mesh Renderer, Mesh Collider etc. Any ideas as to why this isn't working? Any answer would be greatly appreciated, thanks!

 void ColorCast()
 {

     Vector3 offset = new Vector3 (0, 1, 0);

     RaycastHit hit;

     Ray ray = new Ray (transform.position + offset, transform.forward);

     Debug.DrawRay (transform.position + offset, transform.forward * rayLength, Color.red);

     if (Physics.Raycast (ray, out hit, rayLength)) 
     {
         ThePaintableDummyScript objects = hit.transform.GetComponent<ThePaintableDummyScript> ();

         if (objects != null) 
         {
             Material[] mats = objects.GetComponent<MeshRenderer> ().materials;

             foreach (Material mat in mats) 
             {
                 mats [Random.Range (0, mats.Length)].color = new Color (Random.value, Random.value, Random.value, 1f);
             }
         }
     }
 }