User blog comment:Omega natsu2/Chapter 413: The Book of E.N.D., Predictions./@comment-23.117.125.45-20141219030037/@comment-7418318-20141219102355

Not that it'll make much of a difference on the black and while pages of the Manga ^^

But I agree. Though using blue might not be the best choice, since we already had blue flames in the series (Totomaru, formerly of Phantom Lord, used blue, icy flames and Romeo can also use this).

I think neon-ish green might be an interesting colour for END's flames. Something like this even though it isn't flame in that video, but it should give you an idea about the colour I mean.

Or maybe go a bit realistic like this or this. Green fire just has an eery, unreal feeling for me, as if it was just wrong that something like this exists, which makes it perfect for a Demon I think.