Help? Telling difference between purple 'Royalty' and black 'Munger' immature raspberries.

Well, I did a dumb-dumb. I received a couple plants of black Munger raspberries and a couple Royalty purple raspberries. Unlabeled. And while I thought I had kept them sorted, I accidentally mixed them. They are too young to flower or fruit, so I have no idea who is who.  I'm just looking at leaves and stems trying to discern a difference. And kicking myself.

Are there some leaf or stem characteristics that might help me re-sort? If you have any clues or tips (other than label the damn things), then I'm much obliged.

Hi Sara

You are evidently seeing a difference in the two plants, I bet by the color of the leaves, right?

You may have to wait until the plants blooms to see the difference.  

Or you might have to wait until the plants' fruit.

Another way to tell is by when the plants get the fruit.

Can you possibly post pictures of the difference in the leaves so someone might recognize which is which, just from the leaves?