I bought my wife purple led Xigmatek crystal fans for her computer because that's her favorite color. While she is very happy with them, I hate them with a burning passion. They are VERY loud and not pressure optimized. Good case fans if you are one of those weirdos who doesn't mind the noise but I'll never put one in my rig.
Edit: I complained without making a counter recomendation. Since you're looking at crystals, I assume you need to be able to look at and not vomit? That would strike the noctua fans off the list. What color are you looking for, I'll try to help.