Larry
Sounds like TWO things are going on at the same time.
First, genetically, the fish was destined to change as it got older. It just wasn't showing it's "true colors" when you purchased it. Now that you have placed it in your outdoor pond with bright sunlight and black/green surface, it's taking on a darker coloration. I've seen a lot of ochiba that have developed sumi or very dark brownish-black markings. This could all change again as the fish ages. Only time will tell. I have a fish that I purchased two years ago as tosai that was in a 5/$100 group just to put in my Q-tank to keep things going. That fish, when purchased was marked as a doitsu ochiba. Even the dealer said that was what it was. Well, two years later, it is now 17" and has the coloration of a doitsu goshiki. Very, very BLACK with very nice RED. It even has beautiful motoguro. It's not a show fish by any stretch of the imagination, just a pond mutt that has become a family favorite. Try culling those out of your pond, haha!
Mike