Every Star Wars character has an iconic outfit or two. (Or twenty. Hey, Padme.) Obi-Wan has his Jedi robes, Han Solo has his bloodstripe pants and vest, Boba Fett has his armor. Hell, even Chewbacca has his bandolier.
When it comes to Expanded Universe characters – at least those that derive from books, as opposed to more visual mediums like games or comics – things get a little trickier. Authors generally don’t go for detailed descriptions of clothing, so it’s usually pretty up in the air… At least until someone gets on a book cover, or makes an appearance in a comic book. Which is how Mara Jade got the black leather catsuit that has become – like it or not – her trademark.
One other annoying thing about this costume is that it is the only outfit, aside from her Jabba’s palace dancer disguises, with enough references to be accepted by the 501st. So anyone who wants to join the 501st as Mara Jade has to wear the catsuit, basically (though the rebel legion also allows her green outfit).
I also really am not a fan of her magenta lightsaber, but that’s in the books now, so not much to be done. I guess she couldn’t have blue or green because she wasn’t good, but couldn’t have red because she wasn’t a Sith? I just … would rather they’d picked some non-stereotypically-girly color like amber.