How to Fade into black and white in a particular scene?

Super easy. Make a canvas that covers the entire screen and put an image in it that is just pure black. Then use this script on it to fade from black when it starts.

 using UnityEngine;
  using System.Collections;
  using UnityEngine.UI;
  
  public class Fade : MonoBehaviour {
      public float FadeRate;
      private Image image;
      private float targetAlpha;
      // Use this for initialization
      void Start () {
          this.image = this.GetComponent<Image>();
          if(this.image==null)
          {
              Debug.LogError("Error: No image on "+this.name);
          }
          this.targetAlpha = this.image.color.a;
      }
      
      // Update is called once per frame
      void Update () {
          Color curColor = this.image.color;
          float alphaDiff = Mathf.Abs(curColor.a-this.targetAlpha);
          if (alphaDiff>0.0001f)
          {
              curColor.a = Mathf.Lerp(curColor.a,targetAlpha,this.FadeRate*Time.deltaTime);
              this.image.color = curColor;
          }
      }
  
      public void FadeOut()
      {
          this.targetAlpha = 0.0f;
      }
  
      public void FadeIn()
      {
          this.targetAlpha = 1.0f;
      }
  }