I just read a novel in which the protagonist has synaesthesia, which is (baring a spelling mistake or two) the technical term for getting the senses mixed up, or having concepts like days of the week manifest as sensory impressions. The guy loves going to church on account of the colours in the singing, but he dislikes long drives on unpaved roads because of the colour and shape of the sounds of the gravel hitting the underside of the truck. His favorite way to relax is to plug in the vacuum cleaner and feel the clear glass egg of the sound in his hand. The book is A Rhinestone Button by Gail Anderson-Dargatz. It is pretty good but not quite as good as her others, The Cure For Death By Lightning and A Recipe For Bees. Also, Margery Allingham wrote an Albert Campion mystery which hinged on the colours of the days of the week. I think it would be so cool to be able to distinguish chords by their colours.