It's been a *loooong* time since I followed any DC comic storylines, but "the" Green Lantern (Kyle) is actually just one of a large team of guardians who have all been bestowed a "ring of power" and the responsibilities that come with it. If there's now a black character with the same powers and uniform, it's probably just another member of the same group.
IIRC, every planet with life was granted a "Green Lantern" protector -- I seem to recall an alien "Green Lantern" coming to pay a visit in one of the old comics.