FireMonkey provides support for both native styling and custom styling. Part of the current Bonus Pack are eleven premium FireMonkey styles. Choose from Jet, Sterling, Diamond, Emerald Crystal, Emerald Dark, Coral Crystal, Coral Dark, Vapor, Copper, Copper Dark and Radiant styles, optimized for iOS, Android, Windows and Mac application development.
Each style includes the required graphics to ensure the user interface looks great on each supported target platform. For example, this includes 1x, 1.5x, 2x and 3x resolution graphics on Android. We have many great resources to help you get started using custom styles in your multi-device applications.
By adding a style selector to your multi-device application, you give your users the option to select the theme they like best. Click here for the tutorial.
A great collection of style related posts can be found here.