To make the problem visible, please see the attached file. I inserted both macros and put a few shapes onto the slide. The problem shape is Shape 2. It should match with Shape 1, as it seems to have no fill, but it matches with Shape 3, 4 and 5, as in fact it has an (invisible) blue fill.
John's idea with changing RGB (1,1,1) and then making this invisible would solve one half of the problem: Shape 2 would not match any longer with Shape 3, 4 and 5. But it still would not match with Shape 1. Shape 1 really has no fill. I deleted the fill of Shape 1 by using No Fill from the coloring menu, not by using the no-fill-macro.
I was hoping for something like, e.g., oshp.Fill.ForeColor.Delete (which is not the solution)