When you add pcolor plots to an axis, which changes/sets the shading scheme used by the axis, it can sometimes change the way that the properties of other surface objects are interpreted. I've never quite figured out the rhyme or reason for this, but I've found the easiest solution is to manually set all the properties after everything is in place.
In your case, try adding these lines at the end of your code:
set(h, 'linewidth', 5, 'markersize', 15);
set(h, {'markeredgecolor', 'marker'}, {'m' 'o'; 'y' '^'; 'g' 's'});
uistack(h, 'top');
(I increased the marker size because otherwise it's almost impossible to see the marker shape with such a thick line width... is that really what you want?)
On my computer, changing the renderer via
set(gcf, 'renderer', 'zbuffer')
also makes things look a bit better, but that may be OS/graphics card dependent.
