如何在UINavigationController标题视图中自定义后退按钮的文本颜色？

I'm using a custom tintColor on my UINavigationController's navigation bar, and because the color is so light I need to use dark colored text. It's relatively easy to swap out the title view, and the custom buttons I've added on the right hand side, but I can't seem to get a custom view to stick on the back button. This is what I'm trying right now:I'm using a custom tintColor on my UINavigation