Draw always visible global border

Hi I use a lot of virtual machines that have KDE Plasma 5.27.5 KDE Framework version 5.103.0.

I connect with virt Viewer and SPICE protocol. In order to quickly distinguish the VMs from each other I want a global border that is always visible and even if I have a window maximized the border is still visible

Something like this:

An always visible global border that surround the whole Desktop

How can I achieve this ?

It would be perfect to be able to change the color and pixel size of the border

I don’t have a solution for the border - but wouldn’t it be easier to just use different wallpapers (pictures or solid colours) to keep them apart?
The only situation when this will not work is if the wallpaper of a VM is totally covered…

PS: You could also use something like the Media Frame plasmoid and display a picture of the VM’s name floating above all other windows in one of the corners.
Or try if it would be viable to display a full screen picture with the Media Frame plasmoid that is translucid with a coloured border only on top of everything.