TG got it right! No need for me to elaborate on that.
All I can add is that the name means "tea-colored Koi." Perhaps this one's color will lighted as it grows. But being a longfin, it would not actually be considered as a Chagoi, nor is Chagoi by definition, metalic.
If you really want to learn more about "Koi appreciation," do a search using that phrase. There are a lot of good articles on the subject.
But one of the best references on that subject is, in my opinion, Peter Waddington's book, "Koi Kichi." You may be able to find it in the library, possibly thru an inter-library loan. Check with the librarian.
The subject itself is a complicated one. But one worth studying. It is a rather specialized area, but you'll find that just as true when looking at any show oriented animal hobby.
Might try the AKCA web site as well. (Associated Koi Clubs of America.) One web site that I know of right off hand that has a lot of this kind of info is
http://www.nishikigoi-info.com/index.html Look under the heading of Koi types for info on specific varieties.
Mike S.
Spring Hill, FL