For some reason I missed this in the small mention we gave it the first time around, but apparently the Netherdrake mount (which I'm currently grinding like a madman to get the skill for) is available in a bevy of colors! Our friends at WoWHead have posted not only the Tier 6 stats, but also all the different Netherwing mounts.
When the time comes, you'll get your choice of Azure, Cobalt, Onyx, Purple, Veridian (wha?), or Violet dragon mounts. I'm sure Onyx will be a popular choice, but you never know-- paladins might want to go for purple just so it can match with their Tier 5 gear. Unfortunately, all those colors seem really-- blue. Where's my red Netherwing, or my gray dragon? Veridian is actually kind of greenish. Looks pretty blah to me, but whatever floats your flying mount around faster than a mage spell, I guess.
The mount actually comes from
a rep vendor, so as long as you get exalted with whatever quests need to be done, you'll have your pick of the litter. Even though each mount is Unique, I think that only means you can't have two Onyx mounts-- I believe that you'll be able to buy as many different colors as you have the gold for (maybe those of you on the PTR can confirm or deny*-- whoops, see update). Anyway, looks great! What color are you going for?
Update: Word from the PTR says it's actually a quest reward, so one dragon for you. Choose wisely. Also Veridian is apparently a typo-- the color should be viridian. (thanks, kind readers!)
Update2: Now we're being told that you can buy another color after you get your first one. Looks like we'll have to wait and see what happens on the live servers.