I also have a black sand bed. Got it for two reasons, one I thought they looked cool in the other tanks I've seen... and two because I didn't want a dragon goby in there for the extra work I have to go through blasting sand off of coral and rocks.

Additionally I have a shallow bed with only about six or eight of the nasarious snails.

I don't know if they have a darker sand or not but I do get a visible brown dusting on my sand bed that comes and goes periodically. I don't worry that so much as the cyano. I've tested my rodi water and it comes out at 0 ppm, not sure if that measures silica though.

I've seen a lot of really white sand beds on youtube but I wonder how much of that is white and how much of it is reflected light drowning out the color of what lies on the sand to make it snow-like.