How can I display a sub-area border in a map?

Dear All, I created a Lambert Conic Projected map about Europe. I would like to show the border of some subregion. I tried the following code for show the Mid-Europe:

axesm('lambert','maplatlimit',[ 26.5861 71.8699],'maplonlimit',[-34.748 60.8422]);
pcolorm(lat,lon,z);
demcmap(z);
colorbar;
hold on
axesm('lambert','maplatlimit',[44 55],'maplonlimit',[ 16 30]);
S = shaperead('landareas','UseGeoCoords',true);
geoshow([S.Lat],[S.Lon], 'DisplayType', 'Polygon');

I attached the map. It shows the area of Mid-Europe but with beige facecolor. How can I show only the edge of this area?