How do I turn off X-Ray effect on my iPad 9?

Try This.

Open the Settings app.

Tap Accessibility.

Under the "Vision" section, tap Display & Text Size.

Look for the "Invert Colors" section. You will likely see two options:

Smart Invert: This reverses the colors of the display except for images, media, and some apps that use dark color styles.

Classic Invert: This reverses all the colors on the display.

Ensure that both Smart Invert and Classic Invert are switched off (toggled to the left).

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]