Having not really been deep into Viera lore myself I went to check out old stuff and I thought it might be worth knowing, at least for those who were in a position more like my own, that Veena and Rava are not new concepts.. such that unless SE goes out of their way to make them more different than they have been in the past we can look at old FF games and already tell that veena and rava are pretty much skin color shifts.

The Viera (ヴィエラ Viera) are a rabbit-like race that can live three times as long as a Hume, and divided into two subraces: The light-skinned Veena and dark-skinned Rava. The Viera have rabbit or deer-like features, most notably their long ears. Their feet are shaped in such a way that in order to stand they must wear high heels. Their slender forms heighten their senses and speed, and although their defense is low, Viera agility and finesse are unmatched by the other races. In Final Fantasy Tactics Advance, Vieras have blue-white, pale green, or purple-white hair, with only a few having hair that is pure white, which is considered to be a blessing. Viera can listen to the surrounding nature and sense Mist, and can sometimes go berserk from feeling an overwhelmingly vast quantity of active Mist. In Final Fantasy XII, they live in hidden villages deep within the vast forests of Ivalice. The Viera believe themselves to be intimately tied to the "Wood", a part of the forests themselves, and are rarely involved in matters outside the wood. A Viera that moves out of the forest, like Fran, is considered an outcast and dead to her people. Mixed breeds of Veena and Rava Viera have accustomed themselves to coexist within Hume society, dyeing their white hair.
Sounds pretty much like what we have in FFXIV, but the above was written in 2006. (source: Final Fantasy XII Scenario Ultimania)

I still personally prefer when the clans are very different though (hyur like), because .. more options, but the above might give a heavier lean to same shapes different colors.