Board Thread:Questions and Answers/@comment-26123293-20150326234843/@comment-15636815-20150404055119

I answered this question as part of the answer to a different question, so I never posted anything here. :-)

In Storage, black numbers on green backgrounds represent items that do not consume Storage:
 * reward items that are required for later contracts or achievements
 * items purchased with gems

The drawback to this feature is that Storage does not show a quantity if the quantity is 1. Unsellable rewards have the big "Reward" at the bottom, but if you don't remember which unique items were gems purchases, there's no way to tell. I asked the devs to put quantity numbers on everything in Storage for this reason. Maybe they will.