osFinancials5 installs, by default, in the Classic theme. The Material theme (black icons) is used for most of the topics in this documentation. This is set in Theme on the Setup ribbon.

The osFinancials interface will display in the default "English" language. 

osFinancials5 supports 79 different languages and tax regimes languages liked to 87 Sets of Books (databases) which may be downloaded and customised to meet your requirements. 

You may Switch language (Start ribbon) to choose a different language. 

Depending on the Set of Books template downloaded when Creating a Set of Books (Creation wizard); or downloaded from  the Product information → Technical information → Databases page on the osFinancials website); osFinancials will automatically display the interface language of the language file which have already been linked to each Set of Books. (Setup → Access control).