How do I set my theme in the Teacher App on my iOS device?
In Settings, teachers can choose between three app theme options, Light, Dark, and System Settings.
Open User Menu
In the Dashboard, tap the Menu icon.
Tap the Settings link.
Tap the Appearance.
To select preferred theme tap System Settings  reflects the current devices theme, Light Theme  for dark text on light background, and Dark Theme  for light text on a dark background.