The frio theme is currently the default theme of Friendica. It is based on Bootstrap and mobile ready so you can use Friendica in the browser on your smartphone. Users can choose from eight predefined color schemes and can easily apply their own colorization and add personalized background images.
Vier was the default theme of Friendica since version 3.5.
The follow up theme from Duepunto Zero was the Quattro theme.
The old default theme of Friendica until version 3.5 was Duepunto Zero.