Lois had auburn/reddish hair in the Post-Crisis comics until she dyed it black in the early 2000s. This isn't so out of the ordinary.
Yeah, I liked that. Jet black hair is extraordinarily rare among caucasians, yet a remarkable percentage of comic book characters have it - Clark, Lois, Bruce Wayne, even ol' Captain Marvel. To some degree it was probably a comic coloring convention of the 1930s, as you don't see it very often among new characters introduced in the 1960s - not Peter Parker nor any of the Fantastic Four, nor Hal Jordan or Barry Allen nor...you get the idea. That Lois's, at least, was a dye job made a lot of sense.