Turn emoji back to previous default after upgraded to iOS 8.3
You can try holding down on the emoji you want and see if it brings up a menu to pick the skin color like this:
That feature is mainly only available on the more "human" looking emojis. Doing this will now set the default of that emoji to the color you chose, so I guess you could go through all of them and pick the one you want and they should stay as the new default instead of having to pick from the yellow one every time, but there isn't a way to "revert back" to 8.2 and earlier styles.