Hello there Longest1000,
You've posted an issue with your iPhone wallpaper showing "desaturated" and restarting seems to resolve it. The first thing we'd recommend is looking at the wallpaper photo style to see if it is set to something like "Color Wash".
Create a custom iPhone Lock Screen - Apple Support
In that article it explains different customizations you can choose, including a photo style.
Change the clock style on the Lock Screen
You can change the font and color of the date and time on your Lock Screen.
1. Touch and hold the Lock Screen until the Customize button appears at the bottom of the screen.
2. Swipe to go to the Lock Screen you want to change, tap Customize, then tap the Lock Screen image.
3. Tap the time, then choose a font and color.
To reset the date and time, see Change the date and time on iPhone.
If that doesn't seem to resolve what you are seeing, test a different photo to see if the same issue occurs. Also try a photo that is taken with your camera or downloaded from another source. The goal will be to determine if there is a specific underlying cause and rule out what might be part of the problem. Reply back with your findings.
Warm regards.