Find the Themes and Appearance options in the User Preferences menu. Just navigate to your User Icon > Settings > User Preferences, as seen in the gif below:
Appearance
There are three appearance settings to choose from:
Day – manually set the theme to be your preferred day theme
Night – manually set the theme to be your preferred night theme
Automatic – automatically switch between Day and Night depending on your system settings. (i.e. if you system is in dark mode, Supernotes will be in night mode etc.)
There is a quick three-stage switch present in the bottom right-hand corner of the User Menu for easier access to this setting. Or you can use the command prompt like in the gif above to quick switch between day and night mode, just type 'Toggle ...'
Themes
You can select which theme you would like as your preferred day and night theme, using the two dropdowns in the User Preferences menu.
Hydrogen – a light, bright and white theme
Deuterium – a crème, milky and off-white theme
Zinc – a grey, slate and hazy theme
Carbon – a dark, deep and midnight theme