Change the theme in Unmarked

Short answer: Open Settings with ⌘, go to Appearance, and pick one of five themes: Default, Dusk, Tide, Grove, or Ember. Each ships a light and a dark palette, so set System, Light, or Dark to choose which one shows. The theme also carries into Present.

A theme in Unmarked is the color of the page you read and write on: a light palette for bright rooms, a dark one for night. You pick the theme, then pick whether you want light, dark, or whatever the Mac is already doing.

Set the theme

Open Settings with ⌘, (or Unmarked ▸ Settings in the menu bar).
Go to Appearance.
Pick a theme: Default, Dusk, Tide, Grove, or Ember.
Under the same panel, choose System, Light, or Dark.

The change lands right away. There's no apply button and nothing to save.

Light, dark, or follow the Mac

Each theme has both a light and a dark palette built in. The light/dark control decides which one you see:

System follows macOS. When your Mac switches to dark in the evening, Unmarked switches with it.
Light stays on the light palette, all day.
Dark stays on the dark palette, all day.

If you already run your Mac on a day-night schedule, System is the one to pick. It keeps Unmarked in step without you touching it.

The theme covers every view

The palette you pick shows in Read, Write, and Present. Code blocks follow it too: every theme has its own code colors for light and for dark. There's no separate presentation theme to set. Exports don't take the theme: PDF, Word and the styled HTML file use their own fixed style, code colors included.

Note: Theme sets the colors. Fonts are a separate setting under Typography, not Appearance.