I know there are some Oliver Sacks fans on this board smile.
In one of his recent books, Musicophilia, he writes about a composer with "music-color synesthesia" - he would see specific colors when hearing music in different keys. He also talks about other interesting and weird brain differences in musicians, like musical seizures and things like that...

http://www.amazon.com/Musicophilia-Tales-Music-Oliver-Sacks/dp/1400040817

I had day-of-the-week/color synesthesia when I was a kid. Tuesday was definitely green! DD5 has day-of-the-week underwear and they are each a different color. I wonder if she's going to think of Monday as pink when she is older smile