DamageVisual.cs

using UnityEngine;

public class DamageVisual: MonoBehaviour {
    static Material damageMat {
        get {
            if (_damageMat == null) {
                _damageMat = Resources.Load<Material>("Damage-Flash");
                if (_damageMat == null) Debug.LogError("Damage material not found in resources folder!");
            }
            return _damageMat;
        }
    }
    static Material _damageMat;
    [SerializeField] Renderer[] meshes;
    Material[] defaultMats;

    Health health;

    void Awake() {
        if (TryGetComponent<Health>(out var health)) {
            this.health = health;
        } else {
            var inParent = GetComponentInParent<Health>();
            if (inParent != null) health = inParent;
            else Debug.LogError("Couldn't find health component!");
        }

        defaultMats = new Material[meshes.Length];
        for (int i = 0; i < meshes.Length; i++) {
            defaultMats[i] = meshes[i].material;
        }
    }

    void Start() {
        health.OnDamage += OnDamage;
    }

    void OnDamage() {
        foreach (var mesh in meshes) {
            mesh.material = damageMat;
        }
        new Timeout(() => {
            for (int i = 0; i < meshes.Length; i++) {
                meshes[i].material = defaultMats[i];
            }
        }, 0.2f, this);
    }
}