using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(ColorText1(null) ?? "null");

        Console.WriteLine(ColorText1(Colors.Green) ?? "null");

        Console.WriteLine(ColorText2(null) ?? "null");

        Console.WriteLine(ColorText2(Colors.Green) ?? "null");

    }

    public static string ColorText1(Colors? myColor)

    {

        return myColor.HasValue ? ((Colors)myColor).ToString() : null;

    }

    public static string ColorText2(Colors? myColor)

    {

        return myColor?.ToString();

    }

}

​

public enum Colors : byte

{

    Default = 0,

    Red = 1,

    Yellow = 2,

    Green = 3

}

​