Pentakill Yorick has orange spell effects... Pentakill Karthus?

I was thinking, since Karthus has zero skins that actually change his spell effects, wouldn't it be appropriate for Pentakill Karthus to have similar spell colors to Pentakill Yorick? Their base spell effects are identical in color; I think it'd be a fairly simple and nice change to give Karthus some variety with his skin's spell effects, and it'd help tie the Pentakill skins together in more than just name and outward appearance.