The display elements in a Tersus model are using these style classes in two ways:
Copy the definitions of the style classes you wish to change to the stylesheet.css file in your project's web folder. Any change you make there will override their default definitions.
You can also add new style classes and use them in the html.styleClass property of display elements (see example, and also Backgammon on iPhone).
The Theme Editor is a tool to help you change the look and feel of applications in a more user friendly way, including a real time preview of the influence on your application of any change you make. This tool is still in development (available in version 1.3.45 or higher).
iPhone specific style classes are defined in a few files in [studio root]/plugins/tersus.appserver_[version]/DefaultWebapp/styles:
For best results, use the Firefox browser..