React Native UI Kitten is a framework that contains a set of commonly used UI components styled in a similar way. You focus on business logic and it takes care of visual appearance. And the most awesome thing: you can change themes on the fly by just passing a different set of variables.
The main idea of this framework is to move style definitions into specific place making components reusable and styled in a single way. You just focus on business logic and it takes care of visual appearance.