Highlight gameobject

I want to highlight a gameobject only when mouse passes over it. I found a shader that works good when I assign it directly to the gameobject.

But if I assign a script to the gameobject in order to highlight it only when the mouse passes over it, the mesh turns pink. I get the shader from: http://answers.unity3d.com/questions/1068089/unity-520-outlinedsilhouetted-diffuse-shader-probl.html

And this is the script attached to each gameobject to highlight:

using UnityEngine; using System.Collections;

public class HighLighting : MonoBehaviour {

 void OnMouseEnter()
 {
     gameObject.GetComponent<Renderer>().material.shader = Shader.Find("ImageEffectShader");
 }
 void OnMouseExit()
 {
     gameObject.GetComponent<Renderer>().material.shader = Shader.Find("Diffuse");
 }

}