@Cipher7 In the CSS components reference you can see all the used classes. Take the one you want and change any property. You can check the DOM as well. If you have more questions, please open a new thread.
@Mod-Template The best way is to generate your own theme. When you install Onsen UI you’ll get a folder css-components-src like this. Just follow the readme info and then use the generated CSS file in your project.