ColorFader.cs

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class ColorFader : MonoBehaviour 
{
	public float delay = 2;

	void Start () {
		StartCoroutine(Fade(delay));
	}

	IEnumerator Fade(float duration)
	{
		var comp = GetComponent<Image>();
		for (float timer = 0; timer < duration; timer += Time.deltaTime)
		{
			//Debug.Log(timer/duration);
			comp.color = Color.Lerp(Color.black,Color.clear,timer/duration);
			yield return 0;
		}
	}

}