CHROMESTHESIA?

Chromesthesiais a type of synthesia, which means that Dean experiences several pseudo-visual phenomena when he hears various sounds, most often voices and music he likes. He does not actually see anything, nor are his optical nerves being stimulated. His memory of them may be getting foggy. Do not take his word for law if he explains.  

People
♦ Sam: A very bright red that swirls the entire “field of vision.” It can sometimes be a little overwhelming.  

Music
♦ Led Zeppelin: Grey and black fireworks that pulse with the beat.
♦ Queensrÿche: Bright yellow that is very overwhelming but somehow pleasant.