Black and white screen

You might’ve activated Color Filters by mistake.

Enter Settings > Accessibility > Display & Text Size > Color Filters, and turn the slider off. If this does not work, you may have inverted your displays colors.

Enter Settings > Accessibility > Display & Text Size > Classic Invert, and turn the slider off. If neither of these work, consider sending your iPad into a Apple repair center.

If the screen colours appear to be distorted or unnatural, you need to check some key Accessibility settings that are intended to compensate for specific colour-vision issues:

Settings > Accessibility > Display & Text Size

Ensure that all settings enclosed within the red box above are switched OFF/Disabled.

Otherwise, depending upon your installed version of iOS/iPadOS, you’ll need to look at your Dark Mode settings:

Settings > Display & Brightness > [Appearance]