How do i mark the Borders in my CK3-like Province System?

Hi,

I am currently trying to make a Province System like in CK3, but with a Planet as a Map. So I placed 2 Speres in my World: A bigger one as planet surface, and a smaller one inside, which I can paint with different Materials inside UE5. I found a way so My BP recognizes the Material under my click and opens the Widget with the same Name as the Material. This works fine. Now i want to add Borders to my outer Sphere, because at the moment the provinces are invisibile. So I thougth about duplicating the inner sphere, scale it up and adjust the alpha value of the materials. But if I do so my map is coloured everywhere, instead of just marking the Borders. So is there any way of marking just the borders to another material, preferrable letting the Materials do this automatically since i got quite a lot of provinces?

Thanks for every piece of help.