It is possible to set the theme of CG-Button application. The theme affect the general look of views and UI elements on widgets. In the case of managed-app website admin can also determine the default theme for the app running on a website. This is explained in the managed-app users manual.
To change the theme open the main menu and click the Theme button:
The Themes selector is open. Click of theme buttons and see preview of the effect. If you prefer to return to default theme select "Content Glass" theme that is set as the default.
Here are two examples: