One of two built-in themes, included upon installation of Theme Press.
The Splash Theme is included with Theme Press upon installation, and set as the site default theme upon installation. It includes a moderate amount of font, design, and color theming, and is suitable as a base for customization of your own theme.
You'll find it in your list of themes, named as Vanilla.
You won't be able to make any changes directly to the Vanilla theme. Instead, make a copy first, then create a new theme.