Black koi

Of my offspring from two years ago I kept 6 koi, two solid orange and the other four were three colors, orange, black, and white.  The tri-colored ones did not have the deep colors of the original parents and were mostly white but I was hoping that over time I could breed back some beautiful colors. 
   To my surprise one  of the fish spawned and I had hundreds of babies, most of which lived over the winter.  What was a bigger surprise is that most of the Koi are solid black, a few are blue and some are black with a bronze/orange belly.