Prefab array triangle colors being duplicated

Hi,

I am fairly new to Unity and I have an array of trees that I instantiate from a single Prefab. Then, I want to go through each "triangle" of the meshes of those trees (instantiated prefabs), and assign them Colors. What I am seeing is that all the trees are being the same color or likely copies of a "single" one instead of the trees in the arrays. Please see the ChangeColor method below. Maybe is is something fundamental about prefabs that I am missing.

These three trees should not have the same colors in every triangle according to what I am trying to accomplish.

The Start Function is below but I believe the only relevant part here is Instantiate. The rest is in ChangeColor().

 void Start () 
     {    
         counter = 0;
 
         trees = new GameObject[numTrees];
         for(int i = 0; i < numTrees; i++)
         {    
 
             trees [i] = (GameObject)Instantiate (treePrefab, Vector3.zero, Quaternion.identity);
             trees [i] = changeColor (trees [i],i);
         
         }
 
         List<GameObject> points = new List<GameObject>();
         List<int> distances = new List<int>();
         cam = GetComponent<Camera>();
 
         for (int v = 0; v < vertices.Length; v++)
 
         {
             vertices[v].y = Mathf.PerlinNoise((vertices[v].x + this.transform.position.x)/detailScale,
                 (vertices[v].z + this.transform.position.z)/detailScale)*heightScale;
             if(Random.Range(0,100)<1)
             {
 
                 //GameObject newTree = TreePool.getTree();
 
                 GameObject newTree = this.getTree();
 
                 if(newTree != null)
                 {    
 
                     //float x = (Random.insideUnitCircle.x * 5);
                     float dist_x = (Random.insideUnitCircle.x * 200); //OG is 20
                     float dist_z = (Random.insideUnitCircle.y * 200); //OG is 20
 
                     Vector3 treePos = new Vector3 (vertices [v].x + this.transform.position.x,
                         vertices [v].y - 1,
                         vertices [v].z + this.transform.position.z);//+dist_z);
                     newTree.transform.position = treePos;
 
         
     }
 

ChangeColor

 public GameObject changeColor(GameObject tree, int idx){
 
 
         Mesh meshT = tree.GetComponent<MeshFilter>().mesh;
         Vector3[] verticesT = meshT.vertices;
         Color32 currentColor = new Color32();
         int[] triangles = meshT.triangles;
         //meshT.Clear ();
         Color32[] colors = new Color32[triangles.Length];
         //Debug.Log ("NUM OF TRI IS " + triangles.Length);
         Vector3[] verticesModified = new Vector3[triangles.Length];
         int[] trianglesModified = new int[triangles.Length];
         int r=0;
         int g=0;
         int b=0;

         for (int j = 0; j < triangles.Length; j++) {
             // Makes every vertex unique
 
             verticesModified[j] = verticesT[triangles[j]];
             trianglesModified[j] = j;
 
             b = counter++ % 256;
             if (b==255){
                 g += 1;
                 g = g % 256;
             }
             if (g==255 && b==255){
                 r+=1;
                 r=r%256;
             }
 
 //the idx is just for debugging
             if (idx % 2 == 0) {
                 r = r;
                 g = g;
                 b = b;
             } else if (idx % 2 == 1){
                 int t=b;
                 r = t;
                 g = g;
                 b = r;
             }

             currentColor = new Color (
                 r,
                 g,
                 b,
                 255
 
             );
 
             //Debug.Log ("r = " + r + "g = " + g + "r = " + b);
             counter += 1;

             colors [j] = currentColor;
         }
 
 
         //counter += trianglesModified.Length;
 
         // Applyes changes to mesh
         meshT.vertices = verticesModified;
         meshT.triangles = trianglesModified;
         meshT.colors32 = colors;
         //tree.GetComponent<MeshFilter> ().mesh.colors32 = colors;
         tree.GetComponent<MeshFilter> ().mesh= meshT;
         tree.SetActive(false);
 
         return tree;
         //trees[i].SetActive(false);
 
     }

GetTree

 public GameObject getTree()
     {
         for(int i = 0; i < numTrees; i++)
         {
             if(!trees[i].activeSelf)
             {
                 return trees[i];
             }
         }
         return null;
     }

In summary, I cannot figure out why all the tree objects instantiated from the prefab in the trees array showing the same color while I am giving each triangle a unique color?

Thanks so much for your help in advance.