how to set multiple materials using array in the submesh of an object

Question

I'm trying to insert multiple materials into the object's submesh using the array, but I'm not getting

public GameObject[] obj;

//material mat;

public void Color(Material mat) {

    for (int x = 0; x < obj.Count; x++)
        obj[x].GetComponent<MeshRenderer>().sharedMaterials[1] = mat;

    Material[] mats = GetComponent<Renderer>().materials;
    mats[1] = mat;
    GetComponent<Renderer>().materials = mats;

    {
        print("New Material");
    }
}

Answer 1

material mat; 
GetComponent<MeshRenderer> ().sharedMaterials [1] = mat; 
Material[] mats = GetComponent<Renderer>().materials; 
mats[1] = mat; 
GetComponent<Renderer>().materials = mats; 

First error: The class "Material" should be in capital letters. (your code shouldnt compile)

Second error:

GetComponent<MeshRenderer> ().sharedMaterials [1] = mat; 

doesnt do anything. You can not assign that material like this.

The rest of your code looks correct.

1. Did you assign the "mat" in the inspector?
2. Does your mesh even have more than 1 submesh?
3. Do you even want to assign more than 1 material?
4. Whats the error ? Doesnt it compile? Null reference? Nothing happenes?
5. Does your mesh renderer get the materials or does it just look wrong in the 3d view?

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class MaterialArraySetter : MonoBehaviour {

    public Material Material1;

    void Start ()
    {
        Material[] materialsArray = GetComponent<Renderer>().materials;
        materialsArray[1] = Material1;
        GetComponent<Renderer>().materials = materialsArray;

    }

}

EDIT2:

You seem to have compiler errors.