This tiime last year, I noticed I had about 30 baby koi in my pond, and suspect the parents are a pair of black/orange koi about 10 inches in length, that I've had a couple years. Half the babies are very colorful, but the other half are solid dark greenish/black. A year has come and gone, they're now about 3" long, and the black are still black, with the exception that there seems to be a little greying now under their "chin". I keep hoping they'll change color. By this time next year, I anticipate I'll have to thin the herd, and the black, if they are still black, will be the first to go. You can hardly see them in the pond because of their color. Is it common for solid black Koi? Will they change color?