
The Kennel Club Breed Standard asks for a silver grey, mouse grey or roe grey with a small amount of white on the chest is allowed. Silver grey is the preferred colour.
I have never heard of the origin being black but it is thought that the Bloodhound or similar hound was in the make up. Many years ago the KC registered a black littter of Weimaraners but these pups eventually had their registrations declined as there is no way you can get a Black Weimaraner unless it is crossed with a black dog.
You can get a mis marked Weimaraner which has the same tan markings as a Doberman which crop up ever so often and shouldn't be bred from really.
Blue Weimaraners are also in the breed with US imports into the UK although the country of origin ie Germany don't recognise the colour.