In windows, you can change the icon associated with a program or file shortcut. Below are the steps to achieve this.
– Right-click on the desktop icon as shown below
– Select properties
Click on change icon
This will open the change Icon wizard,
– Select your desired icon or browse to a different location and select and icon.
– hit ok
– Apply the changes, or
– Click on ok on the fly as shown below.
Now the Fast User Switching Icon has changed.
See the following link on how to create a desktop shortcut https://techdirectarchive.com/2020/03/08/how-to-create-a-shortcut-in-windows/
For how to make a desktop icon available for all users, see https://techdirectarchive.com/2019/05/11/how-to-make-a-desktop-shortcut-available-for-all-users-in-windows-7-and-10/