The Wood Wasp can come in two different colors, a light green and a dark green, as seen above. This came as quite a surprise to me since I've never seen the darker version in all of my pet battling adventures in Gorgrond. And I used that zone to farm a large portion of the (pre-nerf) 500 Draenor pet battles achievement! So as soon as I read the post on the WarcraftPets forum, I just had to see and collect one for myself.
The Wood Wasps flying around Ruins of the First Bastion area in Gorgrond all have the light green skin. It's hard to say whether or not they can spawn in as the primary pet with the dark green color (I've never encountered one), but it's definitely easier to find one of these if you find a Wood Wasp as a secondary in battle.
If you find a pet battle with a Wood Wasp as a secondary, just forfeit repeatedly until it shows up as the desired color. It took me many, MANY forfeits before I got the dark green wasp to join the battle.
Since pets lose a percentage of their health after each forfeit, the risky part was to make sure my pets had enough health to win the battle even after so many chain-forfeits. Thankfully, the Menagerie level 2 perk reduces the cooldown of Revive Pets to only 4 minutes while in Draenor. Plus I had some bandages on me, with a ton to spare on an alt.
This is certainly a wonderful surprise and I really like the dark green Wood Wasp. If I had to choose, I'd pick that one over the light green one. I'm not sure why. :P