I have two Nexus 8 hubs. One is a "normal" hub and the other is a "premium" (red band). The normal hub was originally lubricated with the darker grease, which I believe is a molybdenum disulfide lube of some sort. The red band was lubed with a white lithium-type grease when I first opened the hub.
For about the last 15 years I have been lubricating each hub by dipping it once a year in gear oil (Royal Purple 75W-140), and lubricating only the hub bearings with the black Nexus grease. The bearing races appear un-worn and the hubs perform normally. There is a total of about 15,000 miles on the hubs... I haven't kept exact records.
So my untrained opinion is that you can safely use the darker grease.
BTW, my grease comes in a tube, not a bottle.