The easiest way is to add MonoBehaviour to the prefab, and use OnMouseUpAsButton.
This way you will be able to modify the marker as if it were a simple GameObject.
https://docs.unity3d.com/ScriptReferenc … utton.html

Or you can use marker events, get an instance, and perform the action you want.
https://infinity-code.com/doxygen/onlin … 20bb0744f5
https://infinity-code.com/doxygen/onlin … 293778120b

Trying to discuss your code is pretty useless because it depends a lot on the context how and where you use it.
But I would recommend not to use GameObject.Find because it is slow and can give you a lot of problems if used incorrectly.

with my code I can change the color of my prefab present in the scene but the clone object under 3d marker does not change and therefore not even on the map! how can i modify it via code, do i need to recover the clone components? can you give me an example, please

I wish I could change colors, materials, transformations,turn off and on parts of the 3d Marker

Thank you very mutch

for example, here I put the code I use to change the color of the 3d Marker when it is clicked

[SerializeField] Material[] material;
    [SerializeField] Renderer rend1;

    void Start()
    {

        rend1 = GameObject.Find("Pin1").GetComponent<Renderer>();
        rend1.enabled = true;
        rend1.sharedMaterial = material[0];

void Update()
    {

     
        if(Input.touchCount>0 && Input.touches[0].phase==TouchPhase.Began)

        {
            Ray ray2 = Camera.main.ScreenPointToRay(Input.touches[0].position);

            RaycastHit hit2;

            if(Physics.Raycast(ray2,out hit2))

            {
                if (hit2.collider.gameObject.tag == "contenuto1")

                {
                   
                    rend1.sharedMaterial = material[1];
   
                    Debug.Log("contenut1");
                }