shooting raycast from each triangle on mesh and change its texture

I dont know it this has been answers, did some searching and came out dry.

Question is that, If I was to have a object with a mesh that contains 200 triangles which make up 100 1x1m squares. I want to change the texture of the squares if an object is directly above that square to indicate where that block above is going to land. Currently I have 100 individual cubes with an attached script that does that by each shooting a ray cast in the air and if it hits a certain object with correct tag it changes it texture. here is the script for further understanding:

 using UnityEngine;
 using System.Collections;
 
 public class TextureChange : MonoBehaviour {
     
     //Texture to change to if ray cast its control block
     public Texture colourChange;
     
     //Its orginal texture to revert back to
     public Texture previousTexture;
     
     
     // Update is called once per frame
     void Update () {
         
         //variable to contain all layers but layer 8
         LayerMask layerMask = 1 << 8;
         layerMask = ~layerMask;
         
         //variable to store raycast values
         RaycastHit hit;
         //if the raycast hit something check objects tag, else keep orignal texture 
         if(Physics.Raycast(transform.position, Vector3.up, out hit, Mathf.Infinity, layerMask.value)) {        
             //if that object has tag control block, change the texture to the colourChange texture
             if(hit.collider.gameObject.tag == "ControlBlock") {
                 //change texture to requested texture variable 
                 gameObject.renderer.material.mainTexture = colourChange;
             }
             //if its an no controlable block keep it as orginal texture
             if(hit.collider.gameObject.tag == "UnControlBlock") {
                 gameObject.renderer.material.mainTexture = previousTexture;
             }
         } else {
             gameObject.renderer.material.mainTexture = previousTexture;    
         }
     }
 }

But having 100 blocks seems wasteful if there is an alternative method. Thankyou if for any answers if there is any on this.