Many devices today have a built-in feature to reduce the amount of blue light from their display. On iPads this feature is called "Night Shift".

Enabling Night Shift mode

To turn on Night Shift mode, first open the Settings app on the iPad.

Tap Display & Brightness on the left side, then tap Night Shift.

You have the option to manually enable Night Shift until the end of the day, or to enable it according to a schedule. When you turn on the Scheduled toggle, you will see controls for setting the time you'd like Night Shift to automatically turn on and off.

You can also control how much blue light is filtered using the Color Temperature slider.