I can't explain why I like blue girls, I just do. So it's pretty darn incredible when there are cosplayers willing to color their skin for certain characters. Here's an alien babe from the "Interstella 5555" anime/album:
Ever since Voltron: Defender of the Universe, I have had a thing for blue women. There was even a scene in which Lisa from the Sea Team, while applying makeup, laments to Cinda, her blue-skinned colleague (from an unspecified water planet) on the Land Team: "*sigh* I wish I were blue..."