I haven't actually seen a black one yet, but it just depends who makes their parts at the time. I come across a couple of the 04 caps now that leak and don't seal properly... In each case I put the old cap back on without issues. My personal opinion is don't change the cap just because of the newer part number... if the old one works and doesn't leak... keep using it. The likelihood of the tank leaking seems to be greater than the cap (from what I've seen)
Goes back to that good old saying, "if it aint broke don't fix it"