Customizing TalkBack requires a basic knowledge of HTML and CSS. If you lack that knowledge, now is as good a time as any to learn. :-)
But I am not your HTML and CSS teacher...it’s up to you to do your homework and learn the basics. Please don’t ask me how to change the style of an element so that it has a different color, font size, etc. I don’t have the time or patience to provide that type of support. Instead do a web search for HTML or CSS and words like tutorial, tips, tricks. You might start with the W3C tutorials.