OK, besides all the girls designs vs. boy designs, I interpret the OP's question as to "are there differences" between genders. I'm only going to address the Depend versions of higher quality pull-ups, RealFits & Silhouettes. I've tried the Silhouettes, and they seemed lackluster, TO ME. My wife had bought them for herself, and I was just trying them on for comparison purposes. In my opinion, the RealFits hold more, fit more snug, and seem to have absorbent materials throughout the diaper, whereas the Silhouettes seemed to concentrate only on the bottom, where more female pee would gather. My trial wasn't scientific, but it made me want to have my wife try my RealFits, to see if she could tell the difference, which I'm not sure she ever did.
As for the color difference, the Silhouettes were pastel pink & blue, while the RealFits are powder blue & gray. Nothing very babyish about either, but a magic marker, and/or some appropriate stickers could make either a bit more childlike, if someone was so inclined. I'm not.
PS - I should have specified that there are other Depend pull-ups out there (refastenables, etc), but the Silhouettes & RealFits usually are only sold in a box, though I did just recently find them in a 20-pack (softpack), but there was no price break for buying 20, so I just bought my typical box...