The story is a modern fantasy and my character is a common college student in the LA area of haitian descent. Is it possible for my character to have naturally red (like a dark red) hair? Or green eyes?
Haitian is a nationality, rather than a race, so yes. If she's white and Haitian (admittedly a relatively rare combination) she can easily have those. If you mean 'can a black woman have naturally red hair and green eyes' then that's a hell of a lot less likely. It can happen, though, either through spontaneous mutation or inherited genes from white ancestors, though she'd need white ancestors on both sides of the family.
I hope so, because I have an MC who has blonde hair, and in her nation they have all have black hair (the genes comes from a Grandmother who comes from a different part of the world)
Considering the involvement of Scotland with the Caribbean slave trade in the 18th and 19th century, I'd think there would be ample genetic impact for it to be possible. It all really depends on the specifics of her genealogy.
Pretty much everyone on Haiti has both black and white ancestors if you go back far enough. Only uncontacted peoples have been isolated long enough not to have any European alleles in their genes. We are all pretty much mutts. Race, as a category of humans, is a social concept more than a biological division between us. And genetically we are quite mixed.
Dunno if this will be of any help, but in trying to find the name of the hair colour (it's Auburn btw) I stumbled across this site: https://howtobearedhead.com/the-6-shades-of-red-hair-which-specific-color-are-you/ For what its worth, it shouldn't matter a whole lot if she has Red hair. Heck, you said it's modern fantasy so she could have green hair and assuming there are enough goblins running around, I'd likely never bat an eyelid.
If she's part White (which is plausible since Haiti used to be a French colony) then yes. I know East Asians can naturally develop shades of red hair and green eyes (although much rarer than, say, Celts) and since most Blacks in North America are 20% White (on average) why not a Haitian who has enough French in her to have red hair and green eyes?
Don't know if she's Haitian specifically, but I imagine she's close to the look you're going for. Spoiler: but who will spoil the spoilers
One of my characters is mixed race (Eurasian), and she has red hair and freckles. Not sure how genetically likely that is, but I like her look, so I don't really care. I say do whatever you want.
A character in Solo called Enfys Nest is clearly black and has what looks like natural red hair, so I'd say yes.
