Whys isnt the gameObjects changing colour?

This script doesn't seem to work for some reason. I've tried col.gameObject.SetActive(false); and that works totally fine. Why isn't the gameObjects changing colour please help!

 private void OnMouseDown()
     {
         foreach (Collider col in colliders)
         {
             
             col.gameObject.GetComponent<SpriteRenderer>().material.color = Color.blue;
             
         }
     }