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);
    }
}