Great Question. Before we give the answer, we need to give you a little history. Years ago (centuries), someone in Eastern Europe (Poland, Lithuania area) decided to see if they could breed an albino (absence of color) swan. So, they began breeding a pair of swans, took their cygnets bred them, took the third generation and bred them, etc., until they ascertained if the swans would have a genetic mutation which could cause an absence of coloring.

What the breeder got was not an albino coloring, but a leucistic (white swan) coloring caused by genetics. At the time, some researchers and taxonomists tried to call the leucistic swan a new species called (Cygnus immutabalis), the changeless swan. However, modern taxonomists declared that the swans were only leucistic in coloring not a new species.

All mute swans are known as (Cygnus olor in Latin Genus and Species name). So, realistically, all mute swans are mute swans. However, breeders and swan specialists call the non-leucistic swans Royal Mutes (because of their black feet and reddish orange beaks. Their offspring are taupe or grey in color). The leucistic swans are known by breeders and swan specialists as Polish Mutes due to their clay colored feet and orange beaks. Their offspring are white in color.

So, to answer your question, your parent swans have carried the normal genetic coloring of taupe for the Royal Mutes in 3 of the cygnets and the leucistic coloring for the Polish mutes in the other 3 cygnets.

This coloration does not mean anything bad for any of the swans and even the Polish Mute swans can and will produce normal genetic colorings in their future generations. The Regal Swan