As Storm-Driver said this is probably an oversight not actually a bug. There is a thread about it here in general. The same skintone mismatch happens on the chest pieces of some of the raid gear (such as the caster body) as well.

Our best bet is if people keep the thread going and hope that it comes to the attention of the Dev team. Under normal circumstances I wouldn't expect a change to the model, but considering that the Neir crossover event has been promoted far more than any other crossover event we have had and they have obviously gone to a great deal of work and care in other aspects maybe we will get lucky this time.