Well, I have a bunch of lower-end black fans, some of them quite old, from before transparent cases were a thing. They're actually pretty much gray if I don't wipe them off.

Noctua's signature... brown-orange? Whatever that color is, it has the same issue. The blades are basically gray if I don't wipe them.

Haven't seen anybody start a gray craze, though. Though I have a grayish motorbike that also shows dust and dirt like nobody's business (it's a bike I use strictly on paved roads).

I have them. They get dusty at about the same rate as a pure black fan (which also shows gray/brown dust quite easily). I need to clean mine about every 6-9 months to keep them looking good enough to "show off". I generally run a Winix HEPA filter in each room of my apartment.

I don't think matte white is worse than matte black in terms of showing dust. They both do.

Black cars show road dust immediately. White cars don't. I image it's similar for computer fans

Dust can actually be more visible on black than on white.