Are black backpacks authorized in the army?

I'm curious, can you clarify for me if black backpacks are indeed authorized for use within the military? It's a detail that I've been wondering about, as I've seen various opinions and regulations floating around. I understand that military regulations can vary greatly depending on the branch, unit, and even the specific mission, so I'm hoping for a general understanding of the policy surrounding the use of black backpacks. Are there any specific guidelines or restrictions that I should be aware of when it comes to this topic?