RAINBOW is VERY HIGH on my list of favorite Ayu songs!!
The "huh huh huh huh" in the beginning got me obsessed with the song for some reason <3 and she has some really good vocals throughout the song as well!
Theres a live version, that she did for CDTV i think, I'll find it on youtube. The background vocals are ~AMAZING~ (not Princess and whatever the other ones name is) XD I'm a freak like that, I obsess over a song for weird things
Got it!
http://www.youtube.com/watch?v=RdhXfT8b0Dw