when you use a Microsoft account to sign in, Windows 10 automatically syncs a number of things to the cloud, including your current desktop theme. Now, as you likely know, a desktop theme includes a wallpaper as well a window color. The sync feature is turned on by default when a Microsoft account is used to log in to Windows 10.
The sync feature comes in handy if you prefer to see the same desktop background and other Windows settings on each and every Windows 10 device.
But then there are users who prefer to customize each of their Windows 10 device in a unique way. For instance, I prefer to set different wallpapers for all my PCs.
If you are using the same Microsoft account on multiple Windows 10 devices but don’t want Windows 10 to sync your desktop wallpaper and theme across all of your Windows 10 devices, you can stop Windows 10 from syncing theme (wallpaper and window border color) across devices. Here is how to do that.
Turning off sync is another way to stop Windows 10 from syncing theme but disabling sync will stop syncing Windows settings and other things as well.
Turn off theme/wallpaper syncing in Windows 10
Step 1: Open Start menu and then click on the Settings icon in the left-side to open Settings app. You can also use Windows logo + I keyboard shortcut to quickly launch Settings app.
Step 2: At the home screen of Settings, click Accounts.
Step 3: Click on Sync your settings.
Step 4: Finally, under Individual sync settings section, turn off the option labelled Theme to stop Windows 10 from syncing your Windows 10 wallpaper across devices.