代码中如何返回IEnumerator？
using System;
using System.Collections;

namespace ConsoleTest
{
    class ColorEnumerator : IEnumerable
    {
        string[] Colors;//实现IEnumerator
        int Position = -1;
        public object Current
        {
            get
            {
                if (Position == -1)
                    throw new InvalidOperationException();
                if (Position == Colors.Length)
                    throw new InvalidOperationException();

                return Colors[Position];
            }
        }
        public bool MoveNext()
        {
            if (Position < Colors.Length - 1)
            {
                Position++;
                return true;
            }
            else
                return false;
        }
        public void Reset() { Position = -1; }
        public ColorEnumerator(string[] theColors)//构造函数
        {
            Colors = new string[theColors.Length];
            for (int i = 0; i < theColors.Length; i++)
                Colors[i] = theColors[i];
        }
    }
    class MyColors : IEnumerable
    { 
        //必须实现IEnumerable接口和实现方法，定义此类型为可枚举类型。
        string[] Colors = new string[3] { "Red", "Yellow", "Blue" };  //定义一个string数组
        public IEnumerator GetEnumerator()
        {