One of the most interesting changes to quest gearing in Warlords of Draenor
is that you have a chance for any item you get as a quest reward to end up upgrading from a quest green to a blue (rare) quality drop, and even an epic (purple) on rare occasions. For example, the Karabor Honor Guard Legguards
are a green quest reward usually. As you can see, they're not
a green for me here, because I got lucky. They're not an earth-shattering upgrade, mind you (although with the stat squish, a few points is a lot bigger than it used to be) but it's still a nice little bump.
You don't have to do anything for this to happen - it's completely out of your hands. It may happen, it may not. Purely from my own experience it's not that uncommon for greens to end up as blues (I've had it happen four or five times) but these are the first epic I've seen on my second playthrough in SMV. Your own rates will vary, of course.