defaultThemeProperty

This property is bound to Tantalum.themeProperty, so if you wish to change the default theme, unbind it, and then either bind it to your own themeProperty, or set its value to your own theme. (the former is preferred, as it allows scenes to be restyled automatically when your themeProperty changes).

New scenes' themeProperty are initially bound to defaultThemeProperty.

If you want to use a different theme for just one scene, you must first unbind Scene.themeProperty, and then set it to the required theme.