Raycasting on specific layers problem

I'm trying to make a raycaster to only cast in a certain layer, but for some reason it's not exactly working.

 IEnumerator MoveToDestination () { 
         foreach (Vector3 nextStep in pathTaken) { 
 
             if (Raycaster.RaycastWithLayerMask (nextStep, Vector2.zero, Mathf.Infinity, 10).collider != null) {
                 Raycaster.RaycastWithLayerMask (nextStep, Vector2.zero, Mathf.Infinity, 10).collider.GetComponent<SpriteRenderer> ().color = new Color (0.0f, 0.0f, 0.0f, 0.0f);
             } else {
                 print ("Raycasting returned null. Tell the dev to fix his shit.");
             }
 
             while (nextStep != transform.position) {
                 transform.position = Vector3.MoveTowards (transform.position, nextStep, speed * Time.deltaTime); 
                 yield return new WaitForEndOfFrame ();
             }
         }
         blockInput = false; //Player is allowed to input new move commands again.
         GetComponent<UnitController>().IsSelected = false;
         PathfinderBase.DestroyAgents();
         yield return new WaitForEndOfFrame();
     }

That is the entire coroutine for context. The problematic part is this:

 if (Raycaster.RaycastWithLayerMask (nextStep, Vector2.zero, Mathf.Infinity, 10).collider != null) {
                 Raycaster.RaycastWithLayerMask (nextStep, Vector2.zero, Mathf.Infinity, 10).collider.GetComponent<SpriteRenderer> ().color = new Color (0.0f, 0.0f, 0.0f, 0.0f);
             } else {
                 print ("Raycasting returned null. Tell the dev to fix his shit.");
             }

I know and specifically checked which layer I want to raycast on, which is 10. For some reason, null is always returned.

As for what I'm trying to do, once a player clicks on a position eligible for moving, an array of Vector3 is returned from that specific pathfinder object, giving a path to it from the player unit. Obviously, each element of that array is a step towards that selected position. Also, upon setting the path, the pathfinder agents become visible, to signify the chosen path to the player. I want them to become invisible again section by section, as the unit starts moving towards each section.