I can't even imagine it for a girl, it's totally masculine to me. Because my first experience with it as a name (or even a word at all, because I was like 8) is from the character in Final Fantasy III(/VI). I remember learning about light in 5th grade and that cyan was a color and I was like, ohhhhh. So anyway, I like it for a boy. It's pronounced like sy-ANNE, never heard it said any other way.
Here's the character I'm talking about so you can see the picture I have in my head from it: (pictures I could find were giant, so here's just a wiki link)
http://finalfantasy.wikia.com/wiki/Cyan_GaramondeThis message was edited 3/31/2012, 3:56 AM