How do I replace white prefaps with red prefabs?

Hi, I want to do something like below.

The purpose is to put the red prefaps instead of the white prefeps removed.

But since I use this code (Instantiate(two,hit.point,Quaternion.identity)), where does the mouse click creating a new one there.

How do I replace white prefaps with red prefabs? (Same coordinates)

for (int x = 0; x < width; x++)
{for (int z = 0; z < height; z++){
GameObject gridPlane = (GameObject)Instantiate(one);
gridPlane.transform.position = new Vector3(gridPlane.transform.position.x + x,
gridPlane.transform.position.y, gridPlane.transform.position.z + z);
grid[x,z] = gridPlane;}}

and,

if(Input.GetMouseButtonDown(0)){
Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
RaycastHit hit;
if (Physics.Raycast (ray, out hit)) {
Destroy (hit.transform.gameObject);
Instantiate(two,hit.point,Quaternion.identity);}}

Hey,

You can just Instantiate the red prefab before destroying the white.

if(Input.GetMouseButtonDown(0)){
       Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
       RaycastHit hit;
       if (Physics.Raycast (ray, out hit)) {
                Instantiate(two,hit.transform.position,hit.transform.rotation);}}
               Destroy (hit.transform.gameObject);
        }
  }

Edit:
Though I suggest using color change which could give better performance as @PizzaPie suggested.

You can count the total number of white box and red box by using a manager script attached to an empty gameObject.

So an example of what the manager script should have.

    public int whiteCount = 0;
    public int redCount = 0;

and within your whitebox or redbox script call

whiteCount += 1;
redCount -= 1;

when you are changing the colors.

To change the material colors, given that you only need two materials, you don’t need a list.

Just add the following to your gameobject script

public Material redMaterial;
public Material whiteMaterial;

and when you know that you want to change the material

hit.transform.gameObject.GetComponent<Renderer>().material = redMaterial;