C#
static void Main(string[] args) { string[] file = File.ReadAllLines("input.txt"); string value = ""; bool defused = true;

        foreach (string cable in file)
        {
            if (cable == file[0])
            {
                continue;
            }
            else
            {
                switch(value) 
                {
                    case "white":
                        if (cable == "white" || cable == "black")
                        {
                            defused = false;                                
                        }
                        break;

                    case "red" :
                            {
                                if (cable != "green")
                                {
                                    defused = false;                                       
                                }
                                break;
                            }

                    case "black" :
                            if (cable == "white" || cable == "green" || cable == "orange")
                            {
                                defused = false;
                            }
                            break;

                    case "orange" :
                            if (cable != "red" || cable != "black")
                            {
                                defused = false;
                            }
                            break;

                    case "green" :
                            if (cable != "orange" || cable != "white")
                            {
                                defused = false;
                            }
                            break;

                    case "purple" :
                            if (cable == "purple" || cable == "green" || cable == "orange" || cable == "white")
                            {
                                defused = false;
                            }
                            break;

                    default:
                            break;
                }

                if (defused == false)
                {
                    Console.WriteLine("Boom");
                    Console.ReadLine();
                    break;
                }
                else
                {
                    value = cable;
                }
            }
        }
        if (defused == true)
        {
            Console.WriteLine("Bomb Defused");
            Console.ReadLine();
        }
    }