Onsen UI is based on Topcoat, you can see the list of components with their code snippets.
http://topcoat.io/topcoat/topcoat-mobile-light.html
Onsen UI add more themes and you can find them at http://onsenui.github.io/topcoat/demo/topcoat-mobile-onsen-ios7.html
Just scroll to the component you want to customize, and click on Show Code Snippets