It's going to be hard to identify them as juveniles because they all look the same. Most LFS will mislabel greens as turquoise depending on what supplier they get them from, but they're almost always greens. The other problem is that some people feel the turquoise are the same as greens, and some people classify them as two separate species.
The turquoise severums tend to come from Peru, along with the rotkiels, so you may have to find a reputable source importing from Peru. Jeff Rapps has them on his stocklist right now.