I don't know that they change a lot, but it is more than zero. I have a normal girl (our first corn) who is now 7 years old. She is slowly darkening, most noticeable when she is getting closer to shedding, but even when she has just shed her colors aren't quite as bright as they were a few years ago. I think that darkening process, especially in an anery that tends to get brown tones as they mature, could easily go in a brownish direction.