There is a farm in WI owned by a man named Dan Powell who raises Hamburgs and he may be able to answer your questions. Also have you done a google search for Hamburg breeders in you area or anywhere. I mean there is a lot of different resources out there. I only have one Hamburg and she is a golden spangled and has slate colored legs. Some day i would love to add the silver splangled Hamburg to my flock because they are so attractive, are very hardy and good foragers and a layers of very nice medium size eggs. I like my hen but the silvers are much more attractive.
And to add to your query, it has been my experience that chickens legs feet and skin color remain constant from birth. In other words I do not think that your bird will have different colored skin, legs, feet as an adult. But that is just my opinion.