So we know there are black Vulcans, and it's fully plausible that just as in humans the ancestors of various species could adapt to local environments, or develop traits via random mutation and sexual selection. But how many species seen have been multi-racial. And how many Vulcans would be black? As Tuvok and his family were the first black Vulcans we had seen up until then, maybe modern Vulcan evolution was reverse to our own, in that Vulcans evolved in temperate climate, but Tuvok's ancestors migrated to a warmer region.
I believe we saw that the Bajorans have multiple races, though we did not often see them played by black actors. IF you accept the old makeup as canon, the Cardassians may have multiple ethnicities, too, though separated on different lines than humans, Vulcans, and Bajorans. (Grey vs. beige, differences in ridge structure.)
Actors of different ethnicities have played Vulcans, Klingons, Romulans, Cardassians, Bajorans, Hirogen, Jem'Hadar, and others. As far as aliens' own ethnicities go, you could divide them up by different makeup designs -- Romulans with ridged foreheads vs. smooth foreheads, Andorians with antennae on the front vs. the back of the head, Trill with spots vs. Trill with forehead bumps, etc. Although it's trickier when a single character's makeup changes over time, like Ensign Ro losing that U-shaped ridge at the top of her nose in her last appearance.
Don't forget the Andorians and Aenar, weren't they two races of the same species? And of course, the Cheronians (half black/half white guys from TOS).
More like two distinct subspecies, akin to modern humans and Neanderthals. Aenar had larger, higher-crowned skulls, differently shaped antenna tips, and telepathic abilities, in addition to being blind and albino.
Now we're getting into the problem of race being a cultural construct, but physical differences are part of what defines a race, so it's unclear to me whether there's a real difference between a race and a sub-species (and I'd call Neanderthals a different species altogether.)
wasn't there an albino Klingon? He might have been from a novel, which I guess from reading these threads isn't canon. Can't remember which novel it was though (I've read so many).
In the DS9 episode with Koloth, Kang, and Kor, there was a villain called The Albino who looked fairly Klingon-ish. But it was never completely clear what race he was. Also, although it was mentioned that Tuvok was the first black Vulcan, in Star Trek V, the Vulcan woman who is shown giving birth to Spock certainly seems to be of black persuasion. Also, in the Next Gen episode The Pegasus, they have a black Romulan, with the same, stupid Moe Howard haircut.
The Albino from "Blood Oath" was mentioned above, but you're probably thinking of "Bernie," a dwarf-albino Klingon-human hybrid from Peter David's first run of Star Trek comics from DC. When PAD was required to abandon that storyline in the comic, he resolved it in the TNG novel Strike Zone, in which Bernie (implicitly) reappeared as Ambassador Kobry.
And don't forget Ziyal on DS9, she was Cardassian/Bajoran. You know what I want to see? And what would make a hell of a hybrid? Klingon/Vulcan mix. Is it even POSSIBLE? (Doubt it!)
It's happened. Remember Ba'el from TNG: "Birthright"? She was a Klingon/Romulan hybrid, and Romulans are Vulcan by species. (EDIT: Oops, just beaten to it.) Non-canonically, in the novels written by William Shatner with Judith & Garfield Reeves-Stevens, Kirk falls in love with Teilani, a member of a genetically engineered Klingon-Romulan hybrid race.
The poor thing will have to pick which race it wants to adopt. I don't think it could successfully live as both a Klingon and a Vulcan. That's like trying to make two magnets with the same polarity stick.
His ears were covered by his hair. I think I did once see a comic book that depicted Klingons with somewhat pointed ears (and bumpy heads, so it was post-TMP), but I can't remember what it was.