Es wird/ wurde gelegentlich die Insel (oder Kontinent) "Vathlo" auf Krypton erwähnt, wo auch Schwarze leben, allerdings vom Rest Kryptons ziemlich unabhängig leben (so'ne schlimme "Seperated but Equal"-Geschichte). In "The Man who has Everything" werden auch "Rassenunruhen" der Leute von Vathlo erwähnt.
In "All-Star Superman" sitzen im Rat von Kandor allerdings mittendrin 'ne Handvoll schwarzer Kryptonier, ohne getrennt zu sein.
Oh, und in Final Crisis gibt's den schwarzen Obama-Superman!!!
PS: Wikipedia sagt folgendes:
"Though previously, "black" Kryptonians were mainly confined within the Kryptonian continent of
Vathlo Island. In the New Earth continuity "black" Kryptonians are more integrated into Kryptonian society than they were in the silver and pre-modern age DC universe. The other racially diverse people of Krypton came from a contient called Twenx. The various silver age versions of Kryptonite have also come back into continuity as they were reduced to only green kryptonite in the post-Crisis universe."
http://en.wikipedia.org/wiki/Krypton_%28…n.27s_revisions