It looks yellow to me also.
You were given a clear answer about another stamp here by perf12:http://goscf.com/t/67517
which said that the color variety listed is black
under UV. Check that, please. Further, you may not know where postal district VII was (I don't offhand), but if you bothered to look at a map, the cities mentioned are nearest the border with Germany and Liechtenstein. Fribourg certainly is not.