Users can choose between a number of built-in color themes. Admins can also provide additional themes and set them as default.
Lemmy is written in Rust, which is an extremely fast language. Thats why it has very low hardware requirements. It can easily run on a Raspberry Pi or similar low-powered hardware. This makes it easy to administrate and keeps costs low.
Lemmy instances and communities can specify which languages can be used for posting. Consider an instance aimed at Spanish users, it would limit the posting language to Spanish so that other languages can't be used. Or an international instance which only allows languages that the admin team understands. Community languages work in the same way, and are restricted to a subset of the instance languages. By default all languages are allowed (including undefined).
Users can also specify which languages they speak, and will only see content in those languages. Lemmy tries to smartly select a default language for new posts if possible. Otherwise you have to specify the language manually.
Lemmy can also function as a blogging platform. Doing this is as simple as creating a community and enabling the option "Only moderators can post to this community". Now only you and other people that you invite can create posts, while everyone else can comment. Like any Lemmy community, it is also possible to follow from other Fediverse platforms and over RSS. For advanced usage it is even possible to use the API and create a different frontend which looks more blog-like.