Bot - Prompt with buttons that disappear and re-prompt if answer not permitted

gistfile1.txt

bot.dialog('/', [
    function (session) {

    var msg = new builder.Message(session)
	.text("Thank you for expressing interest in our premium golf shirt! What color of shirt would you like?")
	.suggestedActions(
		builder.SuggestedActions.create(
				session, [
                    builder.CardAction.imBack(session, "green", "green"),
                    builder.CardAction.imBack(session, "blue", "blue"),
                    builder.CardAction.imBack(session, "red", "red")
				]
			));
        builder.Prompts.text(session, msg);
    },
    function(session, results) {
        var reply = results.response;
        switch(reply.toLowerCase().trim())
            {
            case 'red': case 'blue': case 'green':
                session.send('I like ' +  results.response + ' too!');
                session.endConversation('All done!');
            break;
            default:
                session.send("I'm sorry, that answer is not recognized. Let's try again...");
                session.replaceDialog('/');
        }
       //Shouldn't get here 
    }
]);