Add dual color notification to app?

How do I add a dual color notification icon to my app like this one:

It seems like all apps have this feature except mine. Why? My icon always stays white.

As you can see, the notification is white and then it's in color when the user pulls down the notification bar. Any simple ideas?

My current code:

    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
            .setStyle(new NotificationCompat.BigTextStyle())
            .setSmallIcon(R.drawable.white_icon)
            .setContentTitle("hello")
            .setContentText("test")