Coloration to the beak and the white feathers come along in about 9-12 months of age.
A polish mute cygnet is going to be white in color while a royal mute will be taupe grey.
An adult polish mute will have paler feet, almost light grey brown with a lighter orange beak.
An adult royal mute will have black feet and a bright orange/red beak. The Regal Swan « Hide