There are 2 base themes - light and dark theme. You can choose to follow system theme. Zettel Notes will automatically select light or dark theme based on android system configuration.
You can configure each base theme with
Editor Font and
To configure theme, go to
Settings > Theme.
You can import font
ttf file from storage or use any font from Google Fonts. Read more.
You can configure separate markdown style for light and dark theme. Read more
Following colors are available for changing toolbar. You can select any of them in settings.
Following background colors are supported.