Change MeshRenderer color of prefab instance after creation

Hi Guys,

I'm new to Unity and I've seen a lot of different answers to this question but I can't get any of them to work for me.
I've got a prefab script that creates a quad (from the Unity docs), and I'm using a script to instantiate a bunch of these, and I want each one to have a different color (later they'll have other properties as well).

This is my QuadCreator prefab:

Code (CSharp):

1. public class QuadCreator : MonoBehaviour
2. {
3.     public float width = 1;
4.     public float depth = 1;
5.     public Color color = Color.green;
6.     public GameObject Quad;
7.     public MeshRenderer meshRenderer;
8.  
9.     public void Start()
10.     {
11.         meshRenderer = gameObject.AddComponent<MeshRenderer>();
12.         meshRenderer.material = new Material(Shader.Find("Standard"));
13.         meshRenderer.material.color = color;
14.         MeshFilter meshFilter = gameObject.AddComponent<MeshFilter>();
15.  
16.         Mesh mesh = new Mesh();
17.  
18.         Vector3[] vertices = new Vector3[4]
19.         {
20.             new Vector3(0, 0, 0),
21.             new Vector3(width, 0, 0),
22.             new Vector3(0, 0, depth),
23.             new Vector3(width, 0, depth)
24.         };
25.         mesh.vertices = vertices;
26.  
27.         int[] tris = new int[6]
28.         {
29.             0, 2, 1,
30.             2, 3, 1
31.         };
32.         mesh.triangles = tris;
33.  
34.         Vector3[] normals = new Vector3[4]
35.         {
36.             -Vector3.forward,
37.             -Vector3.forward,
38.             -Vector3.forward,
39.             -Vector3.forward
40.         };
41.         mesh.normals = normals;
42.  
43.         Vector2[] uv = new Vector2[4]
44.         {
45.             new Vector2(0, 0),
46.             new Vector2(1, 0),
47.             new Vector2(0, 1),
48.             new Vector2(1, 1)
49.         };
50.         mesh.uv = uv;
51.         meshFilter.mesh = mesh;
52.     }
53. }

I don't have an actual quad in my scene, the prefab is just the script.
I have a script called Ground that instantiates a bunch of quads like this:

Code (CSharp):

1. public GameObject Quad;
2.     // Start is called before the first frame update
3.     void Start()
4.     {
5.         for(int i = 1; i <= 5; i++)
6.         {
7.             var obj = GameObject.Instantiate(Quad, new Vector3(i*5.0f, -2.5f, -2.5f), Quaternion.identity) as GameObject;
8.             Color col = Random.Range(0, 2) == 1 ? Color.black : Color.white;
9.             var objRenderer = obj.GetComponent<MeshRenderer>();
10.             objRenderer.material.color = col;
11.         }
12.     }

At runtime this creates the 5 quads fine, they're green, but trying to change the color of each instance gives this error:

MissingComponentException: There is no 'MeshRenderer' attached to the "Quad(Clone)" game object, but a script is trying to access it.
You probably need to add a MeshRenderer to the game object "Quad(Clone)". Or your script needs to check if the component is attached before using it.
UnityEngine.Renderer.get_material () (at <0f484ee213264ebc81764f2bdb13f359>:0)
Ground.Start () (at Assets/Scripts/Ground.cs:16)

I've tried using GetComponentsInChildren, I've tried Find... do I need to create the MeshRenderer separately somehow so it can be accessed like this? I'm sure this is something simple but would appreciate any tips