Unity component to replace materials whenever enabled

ReplaceMaterials.cs

// ReplaceMaterial.cs
//
using System.Collections.Generic;
using UnityEngine;

namespace Screenplay
{
    //
    // When enabled, all materials (or all materials matching given original)
    // in this object are replaced with another material.  When disabled, the
    // replacements made are undone.  Can work with all Renderer types in this
    // game object, or optionally all Renderers in all active children of this
    // object.
    //
    public class ReplaceMaterial: MonoBehaviour
    {
        [Tooltip("The material to be replaced; leave None for all materials")]
        public Material original;
        [Tooltip("The material to be used instead of original materials")]
        public Material replacement;
        [Tooltip("If true, all children renderers are affected")]
        public bool children = true;

        public struct Slot
        {
            public int index;
            public Renderer render;
            public Material material;
        }

        private List<Slot> replacements;

        void OnEnable()
        {
            replacements = new List<Slot>();
            Renderer[] renders;
            if (children)
                renders = GetComponentsInChildren<Renderer>();
            else
                renders = GetComponents<Renderer>();
            foreach (Renderer render in renders)
            {
                bool replaced = false;
                Material[] materials = render.sharedMaterials;
                for (int i = 0; i < materials.Length; i++)
                {
                    if (original == null || materials[i] == original)
                    {
                        Slot slot = new Slot();
                        slot.render = render;
                        slot.index = i;
                        slot.material = materials[i];
                        replacements.Add(slot);

                        materials[i] = replacement;
                        replaced = true;
                    }
                }
                if (replaced)
                    render.sharedMaterials = materials;
            }
        }

        void OnDisable()
        {
            if (replacements == null)
                return;
            foreach (Slot slot in replacements)
            {
                Material[] materials = slot.render.sharedMaterials;
                materials[slot.index] = slot.material;
                slot.render.sharedMaterials = materials;
            }
            replacements = null;
        }
    }
}