C# Trigger : test a specific gameobject from public

Hi all !

First of all I must say that I’m a beginner (you’ll see that with my question…)
This is my script, I want to test a specific gameobject in the “public GameObject Cube” (I drag and drop the gameobject I want to test in this field).
In fact it’s working but all gameobjects who get in the trigger work, and I don’t want this, I want only the one I’ve put in the cube field to work and I don"t know how to do it… Thanks for any help !

using UnityEngine;
using System.Collections;

    public class ChangeColorGreen_OnTrigger : MonoBehaviour 
    {
    	public GameObject Cube;
    	// Use this for initialization
    	void OnTriggerEnter (Collider Cube)
    	{
   	Cube.gameObject.renderer.material.color = Color.green;
    	}
    }

you can check if the object in trigger is the same as your other object

 public GameObject TheCube;
        // Use this for initialization
        void OnTriggerEnter (Collider Cube)
        {
         if(Cube.gameObject==TheCube)
          Cube.gameObject.renderer.material.color = Color.green;
        }