Well, I guess that not all Twilight vampires have to be pale from...well, what you just said; Laurent is black. Perhaps whether a vampire becomes pale or not depends on his/her ethnicity. If a vampire was Caucasian or Asian, any ethnic background that allows them to have white skin, then maybe they are the ones who are shockingly pale. However, if a vampire was African-American or Hispanic or any other ethnicity that makes the person have a dark skin color, they keep the skin color they had when they were human. So maybe this explains why Laurent, unlike most vampires, is so dark skinned.
And don't worry, it doesn't sound racist at all! That's actually a pretty good question to me :)
