How can i get my gameobject as a sprite from its collider name?

i want to apply fade effect on my gameobject(in this case,the game object is sprite) only if i touched the object. Im confused how to cast my collider.name to gameobject(sprite).....I can detect the collider name but i cant apply fade effect on them because the parameter in my IEnumerator function is Spriterenderer....please help me

using UnityEngine; using System.Collections;

public class Touch : MonoBehaviour { public SpriteRenderer sprite;

 //Update is called once per frame
 void Update ()
 {
         if (Application.platform == RuntimePlatform.WindowsEditor) // Else if Desktop
         { 
             if (Input.GetMouseButtonDown (0)) 
             {
                 //StartCoroutine(Fade(/*what should i write here*/));
             rayCol();
             }
         }
     }

 private void rayCol()
 {
     Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
     RaycastHit hit = new RaycastHit();
     if(Input.GetMouseButtonDown(0))
     {
         if(Physics.Raycast(ray, out hit)) 
         {
             //what should i write here
             Debug.Log(hit.);
         }
     }

 }

 IEnumerator Fade(SpriteRenderer spriteName)
 {
     for (float f = 1f; f > -0.01f; f -= 0.1f)
     {
         Color c = spriteName.material.color;
         c.a = f;
         spriteName.material.color = c;
         yield return null;
     }
 }

}