Your dashboard
Appearance settings
Bigger text, your preferred units, colors that follow the time of day, and the dimming that protects your television at night.
Where it is
Press Back on the dashboard to open Settings, then choose Appearance, the first item. It is a single page you scroll down.

Theme and Color Palette
The top card. See Themes.
Text and Units
Display Size makes everything on the dashboard larger or smaller. The layout rearranges itself to fit, so pick the size you can read comfortably from your sofa and the cards will still fit.
Units sets Celsius or Fahrenheit, kilometres or miles, for the weather Theatrium fetches itself. Automatic follows the Apple TV's region. Readings that come from Home Assistant keep whatever units Home Assistant uses. (The clock's 12- or 24-hour choice is under Settings › Dashboard › Clock.)
Ambient Theming
Match the time of day: the colors run a touch cooler in the morning and warmer in the evening. Turn it off for one constant look.
Screen Dimming
After a period with no remote presses, the whole screen fades to a dimmer level. Any press brings it back. Choose Dim Screen After (how long to wait) and Dim Level (Slight, Medium or Deep). This is kind to your eyes in a dark room and kind to the television.
Pixel Shift
Move the screen slightly nudges the whole picture a pixel or two every few minutes. You will not notice it while watching, and it stops bright, unchanging shapes such as the clock from sitting on the same spot all evening. It reduces the risk of uneven wear on the screen; it cannot remove it.
Screensaver
The last card on the page chooses what Theatrium shows after a longer idle time. See Screensavers.