iPadOS automatically selects either white or black for the App-icon text - this being determined by the wallpaper or background colour.
If you choose a dark-coloured wallpaper, the icon text should automatically be changed to white. Some bright coloured wallpaper backgrounds (such as your illustrated bright purple-to-blue gradient), will inevitably result in black text labels.
Choosing an appropriate background/wallpaper is always a trade-off between legibility and aesthetics. As for choice of colour, you might benefit from exploring colour theory. There are many available texts that discuss how colours interact in relation to human colour perception. Here is a link to a Wikipedia page to get you started:
https://en.wikipedia.org/wiki/Color_theory
Otherwise, if your iPad is not operating as expected, try a forced-restart - as this will often clear an isolated or post-update software issue:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.
If the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:
How to back up your iPhone, iPad, and iPod touch - Apple Support
When you are happy to proceed, you can perform the reset from iPad settings:
Settings > General > Transfer or Reset iPad > Reset > Reset All Settings
If the problem still doesn’t clear, the next step is to reset the iPad to factory settings:
Restore your iPhone, iPad, or iPod to factory settings - Apple Support
Otherwise, you might be well advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to assist with troubleshooting:
Genius Bar Reservation and Apple Support Options - Apple
