Don't think so. In gonna miss this update because I'm flying on Friday. I know, it could be done today, but that's only one day .
I believe this is only available in 1.7.3 (*Edit, and any version released after), as naming sheep to "jeb_" on the dev server yielded no rainbows.
Oh you know I'm just out 90k blocks in the wild waiting for the update and then I remember theirs the wastelands. Thanks Obama.
So, just learned about rainbow sheep. Before then, 1.7 was awesome. Now, 1.7 is like bacon-fried chicken with lobster stuffing: it sounds like pure amazing.
Not, the wild, but the wastelands. And yes, that means new diamonds, dungeons, abandoned mineshafts, and biomes. Loot away! -Edit: Ninja'd to the max.