App Builder User's Guide Using Themes and Theme Styles 12 Using Themes and Theme Styles Developers can alter a database application's user interface and page layout through themes and theme styles. Using ThemesUse themes and theme styles to increase your productivity when building an application. Managing Themes and SubscriptionsDevelopers can manage themes directly or through the use of theme subscriptions. Creating Custom ThemesCreate a custom theme by modifying existing templates. Using Custom Cascading Style SheetsControl the style of a web page by uploading and referencing a cascading style sheet.