I am pretty sure the sulfur and fire have been crossed to make a black eyed leucistic. I'm not sure about the lemonback. I think Albey made a lemonback pastel that was not like the fire pastel. Dave made a sulfur pastel that was also not like a fire pastel.
The one super sulfur I have seen pics of has a lot of yellow on it.
The super fires I have seen(roughly 60) mostly had some yellow with a few being solid white(to the naked eye).
The only super lemonback I have seen pics of seems pretty white and is described as such by ProExotics.
Super Sulfur
Super Fire
Super Lemonback