NativeScript’s styling infrastructure makes it possible to create and use CSS themes for your native applications, much like you would use a framework like Bootstrap on the web.
The NativeScript project provides a core theme that you can add to any of your projects. The theme includes two color schemes, light and dark, as well as a series of convenience class names to help you build elegant user interfaces quickly.
To customize the core theme Rob Lauer has launched the NativeScript Theme Builder. A quick and easy way to generate NativeScript CSS-based color themes for your next cross-platform native mobile app.