Also im sure you saw sasuke chidori chakra is black now i think now because .now sasuke has access too nature chakra the last time it was black is when used cursed seal level too in thats juugo which is powered by natural chakra.
Sounds legit to me, that's the same reason I assumed the Chidori was black. That and Sasuke told Naruto to use chakra from the Sage to attack so I'd imagine Sasuke did the same.
naruto was able to hurt the limbo madara due to sage abilities.. where as sasuke couldnt.. this is why sasuke left limbo version to naruto.. and told him to use an attack that contained natural energy..