スクリプトで子オブジェクトの色を変える方法

using UnityEngine;
using System.Collections;
using UnityEngine.Networking;

public class TankMovement : NetworkBehaviour {

	public float moveSpeed;
	public float turnSpeed;

	private Rigidbody rb;
	private float movementInputValue;
	private float turnInputValue;

	// ★
	private GameObject tankBody;

	public override void OnStartLocalPlayer(){

		// ★
		tankBody = transform.FindChild("Body").gameObject;
		tankBody.GetComponent<MeshRenderer>().material.color = Color.red;
	}

	void Start () {

		rb = GetComponent<Rigidbody>();
	}

	void Update () {

		movementInputValue = Input.GetAxis("Vertical");
		turnInputValue = Input.GetAxis("Horizontal");
	}

	void FixedUpdate(){

		if(!isLocalPlayer)
			return;

		Move();
		Turn();
	}

	void Move(){
		Vector3 movement = transform.forward * movementInputValue * moveSpeed * Time.deltaTime;

		rb.MovePosition(rb.position + movement);
	}

	void Turn(){
		float turn = turnInputValue * turnSpeed * Time.deltaTime;

		Quaternion turnRotation = Quaternion.Euler(0f, turn, 0f);

		rb.MoveRotation(rb.rotation * turnRotation);
	}
}