I found this while searching for a fix. Here it is, I have no idea whether it will work or not.
How to change the color of the Microsoft App Icon:
You could try this workaround: But, you’ll first need to unlock the Windows 11 taskbar with an App like 'ExplorerPatcher' or similar or edit the registry to unlock it. "Seems to me it's more work than it’s worth."
Normally, app icons from Microsoft store can't be changed. However, a desktop shortcut can be changed to whatever icon you like. The problem is you cannot create a shortcut of an app from the Microsoft store and send it to Desktop. What you could do is this:
1. Create a desktop folder then rename it to whatever you want
2. Drag the app then put it in the folder you created
3. Right click on Taskbar then deselect "Lock the taskbar"
4. Right click on Taskbar> Toolbars> New Toolbar then select the folder you created
5. Right click on the name of the toolbar then change View to Large Icons
6. Right click on the toolbar again then deselect "Show Title" and "Show Text"
7. From there, you can right click on the app then Properties then change it to the icon you like.