How do I change grayscale color settings on my iPad

Try:

Settings / Accessibility / Display & Text Size / Color Filters and set this to OFF

Change display colors on iPad to make it easier to see what’s onscreen - Apple Support

See "Differentiate or tone down colors"

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]