GridGen:

using System;
using UnityEngine;

public class GridGen : MonoBehaviour
{

    [SerializeField] public float cubeSize = 1f;
    [SerializeField] public float cubeVisualSize = 0.8f;

    //[NonSerialized] public int[,,] cubeArray = new int [10, 10, 10]; //old
    private Data3D[,,] cubeArray = new Data3D [10, 10, 10]; //new

    public GameObject linkedObject;

    bool isRunning = false;
    void Start()
    {
        isRunning = true;

        ForAllInGrid((x, y, z) =>
        {
            SetDataAt(x, y, z, new Data3D());
        });

        ReadyCubes();
    }

    //Constructor
    public Data3D GetDataAt(Vector3Int pos )
    {
        return GetDataAt(pos.x, pos.y, pos.z);
    }

    public Data3D GetDataAt(int x, int y, int z)
    {
        return cubeArray[x, y, z];
    }

    public void SetDataAt(int x, int y, int z, Data3D data)
    {
        cubeArray[x, y, z] = data;
        data.locationX = x;
        data.locationX = y;
        data.locationX = z;
    }

    public void SetBlockState(int state, Data3D data)
    {
         data.blockState = state;
    }

    // helper function loop through rows, cols and zees to create a cube of cubes
    void ForAllInGrid(Action<int,int,int> myAction)
    {
        for (int z = 0; z < 10; z++)
        {
            for (int y = 0; y < 10; y++)
            {
                for (int x = 0; x < 10; x++)
                {
                    myAction(x, y, z);
                }
            }
        }
    }//end ForAll

    void ReadyCubes()
    {
        //print("is this working 0");
        if(isRunning == false) return;

        ForAllInGrid((x, y, z) =>
        {
           var gridLocation = GetDataAt(x,y,z);
           var col = gridLocation.blockState == 0 ? new Color32(0,255,0,10) : new Color32(255,0,0,10);

           CreateCubeAt(x, y, z, col);

           //print("is this working 1");
        });
    }

    public void CreateCubeAt(int x, int y, int z, Color col)
    {
        Vector3 pos = new Vector3(cubeSize*x,cubeSize*y,cubeSize*z);
        pos += transform.position;
        Vector3 size = new Vector3(cubeVisualSize,cubeVisualSize,cubeVisualSize);
        var newCube = Instantiate(linkedObject, new Vector3(pos.x, pos.y, pos.z), Quaternion.identity);
        newCube.name = "GridCube " + x + "," + y + ","  + z;
        newCube.GetComponent<GridCubeScript>().gridPosition = new Vector3Int(x, y, z);
        newCube.GetComponent<Renderer>().material.color = col;

        //print("is this working 2");
    }//end CreateCube

}//end class

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Player:

using UnityEngine;
using System;

public class Player : MonoBehaviour
{
    [SerializeField] private GridGen gridGen;

    [NonSerialized] Vector3Int gridPosition = new Vector3Int(0,1,0);

    // Start is called before the first frame update
    void Start()
    {
        this.transform.position = gridPosition;
    }

    // Update is called once per frame
    void Update()
    {
        if(Input.GetKeyDown(KeyCode.D))
        {

            Data3D nextLocation = gridGen.GetDataAt(gridPosition.x+1, gridPosition.y, gridPosition.z);

            if(nextLocation.blockState == 0)
            {
                transform.Translate(Vector3.right * gridGen.cubeSize);
                gridPosition.x++;
            }
            else
            {
                print("can't move there D");

            }
        }

    }//end update
}//end class

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GridCubeScript:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System;

public class GridCubeScript : MonoBehaviour
{
    [SerializeField] private GameObject gridGen;

    [NonSerialized] public GameObject touchingObj;

    [NonSerialized] public bool keepForMoving = false;

    [NonSerialized] public Vector3Int gridPosition;



    private void OnTriggerEnter(Collider other)
    {
        if(other.GetComponent<ObjectPropertiesScript>().wall == true || other.GetComponent<ObjectPropertiesScript>().floor == true)
        {
            Data3D data = gridGen.GetComponent<GridGen>().GetDataAt(gridPosition);
            gridGen.GetComponent<GridGen>().SetBlockState(1, data); // 0 = walkable, 1 = blocked, 2 = keep collision detection

            this.GetComponent<Renderer>().material.color = new Color32(255,0,0,50);
        }
        if(other.GetComponent<ObjectPropertiesScript>().floor == true)
        {
            Data3D data = gridGen.GetComponent<GridGen>().GetDataAt(gridPosition);
            gridGen.GetComponent<GridGen>().SetBlockState(1, data); // 0 = walkable, 1 = blocked, 2 = keep collision detection

            this.GetComponent<Renderer>().material.color = new Color32(100,0,0,50);
        }

        touchingObj = other.gameObject;
        //print(touchingObj.name + this.name);
    }

    private void OnTriggerExit(Collider other)
    {
            Data3D data = gridGen.GetComponent<GridGen>().GetDataAt(gridPosition);
            gridGen.GetComponent<GridGen>().SetBlockState(0, data); // 0 = walkable, 1 = blocked, 2 = keep collision detection

        this.GetComponent<Renderer>().material.color = new Color32(255,255,255,50);
    }
}//end class

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Data3D:

public class Data3D
{
    // 0 = walkable, 1 = blocked, 2 = keep collision detection
    public int blockState = 0;
    public int locationX;
    public int locationY;
    public int locationZ;
}