Program.cs

    class Program
    {
        const string OUTPUT = (string)Extensions.Null;
        static void Main(string[] args) { }
    }

    class Extensions
    {
        public const Extensions Null = null;
        const string s = "255,0,0:0,255,0;0,0,255:255,255,255";
        public static explicit operator string(Extensions _)
        {
            return s;
        }
    }