The color is not a fade, but it does look different in different light. The full Trek color name is Gloss Ice Inkwell Glue.

The roller clutch hub was not very popular on most bikes, though they have some unique advantages. They're completely silent, so no click-click-click as you coast along. For that reason, I understand they were common on police bicycles. They were also fitted to 750 only (at least in 1997). 730 and below had regular ratchet-and-pawl freehubs or freewheels. Another advantage is engagement is nearly instantaneous regardless of the position of your pedals. You don't have to pedal forward to engage one of the ratcheting pawls; the roller clutch is "on" nearly immediately when the freehub body moves forward.

It's Shimano FH-R050. I think it was an Acera or Alivio level component back in the day. I'm not sure if any modern hubs like it, though I'm sure there are niche ones out there.