Yes you are correct. They are the same breed but different colour mutations. However not all mutation colours are recognised for showing and not every breed has that range of colours. For example, Dewlap Toulouse are usually only available in Grey or Buff.
If you are talking about the Americans , those are the colors. Dave Holderread still currently has the the American Lavenders and Blues. Have had all of the colors and their temperments or at least mine were the same as my Sebastopol geese. Wonderful birds to be around.