Changing SpriteRenderer color with UnityEvent.Event

I want to set a color from an spriteRenderer-object by using UnityEvent in the inspector, however there is no color property in the dropdown menu of the target Sprite.

 public UnityEvent OnActivated;
 public bool activated;

 void Update(){
     if(!activated && Input.GetButtonDown("Fire1")){
         activated = true;
         OnActivated.Invoke();
     }
 }