I wanted to make my youtube different in style, more clean and prettier, so I searched for themes and how to do it. I found the solution, but as I couldn't see many talking about it, I decided to organized themes that I liked the most and share how to use it and also save it on github to use later in case of loss.

• First install the extension "youtube tweaks".
  

• Second copy the css from the theme you would like to use, it is separated in the directory themes

• Third open the extension, click on it and go to options page
  

After that you will see an option called custom css and js, there you can make custom scripts in javascript to use and all, but we are going to use only the css part for customization.

After that paste all the css in the css box and click save, you will see the changes applied immediately.

The themes I saved here are from these repositories leaftube darkrange