The color of triangle is not changing when the face of triangle is selected, Any idea why?

Question

I wrote a method for debugging my object in unity. Where I can see which face of the triangle I am looking by using unity RayCast. I can select the triangle i want to but the color of the selected triangle's face is not changing. Below is my implementation with the image:

image from unity sceen

using System.Linq;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;


public class MyRayDraw : MonoBehaviour
{
    public GameObject spherePrefab;

    // Better to reference those already in the Inspector
    [SerializeField] private MeshFilter meshFilter;
    [SerializeField] private MeshRenderer meshRenderer;
    [SerializeField] private MeshCollider meshCollider;

    private Mesh mesh;

    private void Awake()
    {
        if (!meshFilter) meshFilter = GetComponent<MeshFilter>();
        if (!meshRenderer) meshRenderer = GetComponent<MeshRenderer>();
        if (!meshCollider) meshCollider = GetComponent<MeshCollider>();

        mesh = meshFilter.mesh;

        // create new colors array where the colors will be created
        var colors = new Color[mesh.vertices.Length];
        for(var i = 0; i < colors.Length; i++)
        {
            colors[i] = new Color(1f, 0f, 0.07f);
        }

        // assign the array of colors to the Mesh.
        mesh.colors = colors;

    }

    private void Update()
    {
        if (!Input.GetMouseButtonDown(0)) return;

        var ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        RaycastHit hit;


        if (Physics.Raycast(ray, out hit))
        {
            Debug.Log(hit.triangleIndex);
            //cube.transform.position = hit.point;

            // Get current vertices, triangles, uvs and colors
            var vertices = mesh.vertices;
            var triangles = mesh.triangles;
            //var uv = _mesh.uv;
            var colors = mesh.colors;

            // Get the vert indices for this triangle
            var vertIndex_1 = triangles[hit.triangleIndex * 3 + 0];
            var vertIndex_2 = triangles[hit.triangleIndex * 3 + 1];
            var vertIndex_3 = triangles[hit.triangleIndex * 3 + 2];

            // Get the positions for the vertices
            var vertPos_1 = vertices[vertIndex_1];
            var vertPos_2 = vertices[vertIndex_2];
            var vertPos_3 = vertices[vertIndex_3];
            
            // Now for all three vertices we first check if any other triangle if using it
            // by simply count how often the indices are used in the triangles list
            var verticesOccur_1 = 0;
            var verticesOccur_2 = 0;
            var verticesOccur_3 = 0;

            for (var i = 0; i < triangles.Length; i++)
            {
                if (triangles[i] == vertIndex_1) verticesOccur_1++;
                if (triangles[i] == vertIndex_2) verticesOccur_2++;
                if (triangles[i] == vertIndex_3) verticesOccur_3++;
            }
            

            // Create copied Lists so we can dynamically add entries
            var newVertices = vertices.ToList();
            var newTriangles = triangles.ToList();
            //var newUV = uv.ToList();
            var newColors = colors.ToList();

            // Now if a vertex is shared we need to add a new individual vertex
            // and also an according entry for the color array
            // and update the vertex index
            // otherwise we will simply use the vertex we already have
            if (verticesOccur_1 >= 1)
            {

                newVertices.Add(vertPos_1);
               // newUV.Add(vert1UV);
                newColors.Add(Color.green);
                vertIndex_1 = newVertices.Count - 1;
            }

            if (verticesOccur_2 >= 1)
            {
                newVertices.Add(vertPos_2);
                //newUV.Add(vert2UV);
                newColors.Add(Color.green);
                vertIndex_2 = newVertices.Count - 1;
            }

            if (verticesOccur_3 >= 1)
            {
                newVertices.Add(vertPos_3);
                //newUV.Add(vert3UV);
                newColors.Add(Color.green);
                vertIndex_3 = newVertices.Count - 1;
            }


        // Update the indices of the hit triangle to use the (eventually) new
            // vertices instead
            triangles[hit.triangleIndex * 3 + 0] = vertIndex_1;
            triangles[hit.triangleIndex * 3 + 1] = vertIndex_2;
            triangles[hit.triangleIndex * 3 + 2] = vertIndex_3;
            
            // Now we can simply add the new triangle
            newTriangles.Add(vertIndex_1);
            newTriangles.Add(vertIndex_2);
            newTriangles.Add(vertIndex_3);
            
            // And update the mesh
            mesh.vertices = newVertices.ToArray();
            mesh.triangles = newTriangles.ToArray();
            //_mesh.uv = newUV.ToArray();
            mesh.colors = newColors.ToArray();
            


            // color these vertices
            newColors[vertIndex_1] = Color.red;
            newColors[vertIndex_2] = Color.red;
            newColors[vertIndex_3] = Color.red;

            // Recalculate the normals
            mesh.RecalculateNormals();
        }
        else
        {
            Debug.Log("no hit");
        }
    }
}

I have tried to look for the problem, but could not find anything, may you please guide me why it is not changing or what wrong am i doing?