I've had Mavic ceramic road rims on my Litespeed for over 13 years and they seem unworn. These are not really black, but dark gray. For the first thousand miles or so they went through brake pads (Ultegra) like crazy, like every 200 miles. I do not use these in the rain.
So when my commuter bike rims looked thin this summer, I decided to replace them with Mavic ceramic. These look pretty dark, nearly black, and they seem easier on the brake pads (Ultegra and Kool-Stop combo). I shall see if these hold up during the rainy winter commute season and provide decent wet braking power (I can change pads to Kool-stop salmon all around, or Kool-stop ceramic pads).
I'm not so worried about the color, but longevity in the wet and braking power. Staying dark tells me the rim isn't wearing away.