What color is Rogue's hair?

It depends on what you're talking about (comics, movies, cartoons, etc.) and which universe, but if you're talking about the main comicverse, then her hair is said to be auburn, though depending on the artist, it's sometimes shown as regular brown. However it is still claimed to be auburn.

It also depends on the time/era of whatever you're looking at and what kind of ink they felt like using. Hell, in the animated series, her hair color could switch from episode to episode.