not talking about your white (being caucasian, i tan brown.) friends though, im talking about an entire culture trapped in suits for hundreds of years living in space ships with little to no direct sun exposure... We caucasians are white orignally because we didnt get as much sun exposure as other races... but its your preference and still a good pic so whatevs lol.
Biologically skin becomes darker BECAUSE of sunlight exposure. A lack of sunlight exposure would make them white. Black girls are sexier because their skin is darker. Its even more awesome when we get into exotic alien skin colors like gray and night space black.
Lol my white friends example was probably a poor one, anywho, the point I was trying to make was that she's an alien and not a human. A number of reasons (aside from my personal preference ) could allow for a darker skin tone, like pigment colour specific to the Quarians, like how the Asari are blue. Not to mention 4 to 5 generations worth of space faring isn't exactly long, relative to their 50, 000+ years (at the very least) of existence. To me at least, it doesn't seem like they would suddenly turn white if they indeed did have dark skin/skin pigment to begin with, lol.
That's my reasoning anyway! Good fun discussion though, thanks for hanging around!