A Simple Script to change the materials on a game object and all the nested children

MaterialChanger.cs

//  A Simple Script to change the materials on a game object and all the nested children
//  Author: Ashkan Ashtiani
//  Github: https://github.com/3dln/material_changer

using System.Collections.Generic;
using UnityEngine;

namespace TDLN
{
    public class MaterialChanger : MonoBehaviour
    {

        //  The material which we want to change to
        public Material rMaterial;

        //  List of all materials in SkinnedMeshRenderer components
        private List<Material[]> smrMaterials;
        //  List of all materials in MeshRenderer components
        private List<Material[]> mrMaterials;
        //  To check if materials are swapped or not
        private bool hasDefaultMats = true;

        void Start()
        {          
            smrMaterials = new List<Material[]>();
            mrMaterials = new List<Material[]>();
            //Reading all the materials to reapply them later 
            ReadAllMaterials();
        }     

        private void ReadAllMaterials()
        {
            //  First we read all the materials in skinnedmeshrenderer components
            SkinnedMeshRenderer[] skins = GetComponentsInChildren<SkinnedMeshRenderer>();
            foreach (SkinnedMeshRenderer skin in skins)
            {
                if (skin.material != null)
                {
                    smrMaterials.Add(skin.materials);
                }
            }

            // Then we read all the materials in MeshRenderer components and save them for later use
            MeshRenderer[] meshRenderers = GetComponentsInChildren<MeshRenderer>();
            foreach (MeshRenderer meshRenderer in meshRenderers)
            {
                if (meshRenderer.material != null)
                {
                    mrMaterials.Add(meshRenderer.materials);
                }
            }
        }

        private void ReplaceAllMaterials()
        {
            hasDefaultMats = false;
          
            SkinnedMeshRenderer[] skins = GetComponentsInChildren<SkinnedMeshRenderer>();
            foreach (SkinnedMeshRenderer skin in skins)
            {
                if (skin.material != null)
                {
                    Material[] _mats = new Material[skin.materials.Length];
                    for (int i = 0; i < _mats.Length; i++)
                    {
                        _mats[i] = rMaterial;
                    }
                    skin.materials = _mats;
                }
            }

            MeshRenderer[] meshRenderers = GetComponentsInChildren<MeshRenderer>();
            foreach (MeshRenderer meshRenderer in meshRenderers)
            {
                if (meshRenderer.material != null)
                {
                    Material[] _mats = new Material[meshRenderer.materials.Length];
                    for (int i = 0; i < _mats.Length; i++)
                    {
                        _mats[i] = rMaterial;
                    }
                    meshRenderer.materials = _mats;
                }
            }
        }

        private void ReapplyMaterials()
        {
            hasDefaultMats = true;
         
            SkinnedMeshRenderer[] skins = GetComponentsInChildren<SkinnedMeshRenderer>();
            int i = 0;
            foreach (SkinnedMeshRenderer skin in skins)
            {
                skin.materials = smrMaterials[i];
                i++;
            }

            MeshRenderer[] meshRenderers = GetComponentsInChildren<MeshRenderer>();
            i = 0;
            foreach (MeshRenderer meshRenderer in meshRenderers)
            {
                meshRenderer.materials = mrMaterials[i];
                i++;
            }
        }

        public void SwapAllMaterials()
        {
            if (hasDefaultMats)
                ReplaceAllMaterials();
            else
                ReapplyMaterials();
        }
    }
}