I have the map of a country which has different regions on it. I would like to color the borders of some of those regions differently from the rest of the borders. Is it possible?

I know I can create a 0-1 variable that specifies which regions’ borders have to be plotted differently but I have not been able to find the function in geom_sf that could do the trick.

I have seen how to plot the outside/inner borders of the whole country but not specific region borders.

Thanks in advance,