Unity C# - Full Screen Fade
You would think as common as fade transitions are there would be a simple fade command but there is not. Fortunately there is an easy manual way to do it.
Using GetComponent SpriteRenderer Color, you simply designate the alpha value a variable. Simply decrease that value over time and the object the script is attached to becomes more and more translucent.
As an added bonus, you will see how to use Time.deltatime.