[KITKAT]

I think this comment was correct, but you misunderstood what was being said, or the person who repeated it to you misunderstood.

When frozen mice are taken from the freezer, a black belly can indicate that they have thawed and decomposed. The milk in the belly of a pinkie can turn a dark color first, as the first sign that there has been thawing.

Therefore, a frozen pinkie with a black belly can indicate a problem in storage and should not be fed.

Just my .02!