Recessive white can occur with any base. Extended black is no more common in recessive whites than any other base. In my experience e^b is pretty common with white silkies--because silkies are usually e^b based.
The blue bird has a parent that is wither blue or splash, and at least one parent has feathered legs.
The bird on the left comes from a breeding where neither parent had feathered legs (unless one was very sparcely feathered).
Neither have crests, so I doubt they came from silkie or polish breeding. Except that the blue one does appear to have black skin (verify this by looking at wing pits and/or vent area, where there is little feathering. A bird with a silkie parent should have extra toes.