I made a synthetic solution, for which I will attach the calculator with all the reagents used, and something is precipitating out as a dark green/blue color. I mixed the cyanide species separately and the other reagents separately. However, once I added them together the solution turned to a dark green color and once I added the sulfuric acid it became even darker. I believe the precipitate has to do with the copper and iron because I analyzed the solution and there was no copper in it and very little iron compared to the amount of compound added.
Both cobalt and copper would certainly produce that color both in solution and in a precipitate.