How to customize "back" button of a Navigation View?

Hi, I'm using navigationView so "back" btn is appeared at the titlebar. What I want to do is displaying custom background to that highlighted "titlebar" and "back button". Much appreciate your helps :)

Code:

---

Ext.define("Demo.view.Course", {
    extend: 'Ext.navigation.View',
    xtype: 'course',
    requires: ['Ext.TitleBar','Ext.navigation.View'],
   
    config: {
        iconCls: 'courses',
        items:[
            {
                xtype: 'container',
                layout: 'vbox',

                title: "Custom Titlebar",
               
                items: [
                    banner,slider,a,b
                ]
            }
        ]
    }
 });

---

So you want a different background to the navigation bar?

Thanks for your time and care :) I found the solution by using the same answer u gave at this post!