User blog comment:Squedswag/E.N.D. Theory: Possibly that Nasu will stay alive even if he kills Zeref/@comment-30338537-20170107114421

I doubt the colouring given to his Magic in the anime would be the key to any serious plot developments.

Besides, the purple "Magic" may be the standard colour of that absorption device and not have anything to do with the DS it is used on.

Furthermore, Demons have Curse power not Magic, although some can use Magic as well. So the Edolas ppl wouldn't even be able to extract Curse power, as they are only interested in Magic.

Then there is of course the thing of Natsu activating his Demon power long after the Edolas Arc, pretty much confirming the Demon Seed is still inside of him and that it still works.

They will likely find some cheesy way to let him escape death.