Trying to get a sprite to flash a color when hit,Error when trying to get sprite to flash a color when hit

Questions & Answers
1

private SpriteRenderer _renderer;

IEnumerator colorFlash() {
_renderer.material.color = Color.red;
yield return new WaitForSeconds(1);
_renderer.material.color = Color.white;
}

private void OnTriggerEnter2D(Collider2D collision) {
    if (collision.gameObject.tag ==  "EnemyBullet") {
        Debug.Log("hit");
        colorFlash();
        currentPlayerHealth--;
    }
},private SpriteRenderer _renderer;

IEnumerator colorFlash() {
_renderer.material.color = Color.red;
yield return new WaitForSeconds(1);
_renderer.material.color = Color.white;
}

private void OnTriggerEnter2D(Collider2D collision) {
    if (collision.gameObject.tag ==  "EnemyBullet") {
        Debug.Log("hit");
        colorFlash();
        currentPlayerHealth--;
    }
}