What darker colors?
And the thing currently is it's kinda stuff being shuffled around.
On live, male DKs have a dark green, lilac and blueish black (the latter two colors being the ones that got removed from regular player night elves this build)
On live, female DKs have dark green, neon purple and neon pink (the latter two colors being the ones that regular player night elves can still use this build
So if this is the way it's intended, it means female NE DKs get the same hair colors that male DKs had while their original hair colors were given to regular players.
Personally, I think lilac and bluish black fit regular Night Elves much more than neon purple and neon pink, though.