Change Variable on Raycast Hits something else?

I have blocks where they highlight when hit, but I'm struggling to figure out on how to turn off the highlighting after I'm no longer looking at the block.

For example: You approach a chest, it highlights blue. Then when you back away it returns to normal.

Here's what I have so far:

 using UnityEngine;
 using System.Collections;
 
 public class Interaction : MonoBehaviour {
 
     // Update is called once per frame
     void Update () {
         Ray ray = Camera.main.ViewportPointToRay(new Vector3(0.5f,0.5f,0f));
         RaycastHit hit;
 
         if (Physics.Raycast(ray, out hit, 3)){
 
            if (hit.transform.gameObject.tag == "Block") {
                 hit.transform.gameObject.GetComponent<BlockStats>().Highlight();
 
                 if (Input.GetKeyDown(KeyCode.E)) {
                     hit.transform.gameObject.GetComponent<BlockStats>().RemoveHealth(50);
                 }
            } 
         }
     }
 }

and the script that gets called...

 using UnityEngine;
 using System.Collections;
 
 public class BlockStats : MonoBehaviour {
 
     public int Health = 100;
     public bool isHighlighted;
     public Material highlightMaterial;
     public Material startMaterial; 
     
     void Start () {
         startMaterial = gameObject.GetComponent<Renderer>().material;
     }
 
     public void Highlight () {
         gameObject.GetComponent<Renderer>().material = highlightMaterial;
         Invoke ("Unhighlight", 0.5f);
     }
 
     public void Unhighlight () {
         gameObject.GetComponent<Renderer>().material = startMaterial;
     }
 
     public void RemoveHealth (int dmg) {
         Health -= dmg;
         if (Health <= 0) {
             gameObject.SetActive(false);
         }
     }
 
 }

Thanks for the help. Probably overthinking this.