That smokeless powders don't need to be grey, or, more specifically, graphite colored to function. The graphite is just a coating for antistatic and metering characteristics.
Yes, I've read about "poudre blanc", and have seen pictures of yellowish brown cordite, and have seen white nitrocellulose flash paper, but it wasn't until I just recently saw a Vihtavouri production video where I saw my favorite propellants coming out of the extruder looking whiter than rice noodles that it hit me that, yeah, black powder is black because one of it's constituent ingredients is that color, but nitrocellulose, nitroglycerin and the other stuff that affect burn characteristics in smokeless are anything but black.
I just cut open a grain of VV N320, and sure enough the gray is just skin deep. The interior is an off white to slightly yellow color.
Maybe this isn't an "aha!", for me it's still a "huh, well, I'll be..." moment.