The name `Fade' does not exist in the current context

Hi, trying to create a simple change infog colour for my day / night transitions, however fade dose not seam to exist.

 using UnityEngine;
 using System.Collections;
 
 
 public class NightDay : MonoBehaviour {
 
 
     public float delay; // the time that day or night lasts.
     public float speed; // the time the change from day to night lasts.
 
 
     IEnumerator Start ()
 {
         RenderSettings.fog = true;
         yield return new WaitForSeconds (delay);
         StartCoroutine(Fade.RenderSettings.fog.use.Colors(renderer.material, Color.black, Color.white, speed, EaseType.InOut));
         }
     }