Synesthesia (in Greek, the joining of the senses) is a phenomenon in which activation of one sensory reaction involuntarily causes another.  I actually have this.  In my case, when I hear music, I often perceive a color as well.  I have iTunes playlists categorized by color.  There are various types of synesthesia, such as seeing letters or numbers as colors, some people can even taste sounds or colors. I also remember when I was a kid that certain street signs affected my mood.  But it could also be possible that my mom was dosing my juice boxes with LSD.