Unity Engine set Active random Child Object

Question

I want to make an Apocalypse Game and have a Zombie Model with different Materials as Children, I want to randomly activate them, wehn the Zombie spawns (in void start)

I have tried different options, like this:

public class RandomSkin : MonoBehaviour
{
    public GameObject Zombie;

    void Start()
    {
        int randomChildIdx = Random.Range(0, Zombie.transform.childCount);
        Transform randomChild = Zombie.transform.GetChild(randomChildIdx);
    }
}