Wonderfully-titled and very interesting documentary on synaesthesia, courtesy of Google videos.
To see how this relates to the psychological/ philosophical functionalist theory of consciousness, you might want to see this part of the essay I uploaded a while ago onto this site. If I’m right, synaesthesia might be a key way of testing (and refuting) functionalist theories of consciousness.
Note: the possible refutation itself comes from Jeffrey Gray et al’s series of empirical psychological papers from the early 2000s – you can get a flavour of these by typing in his name and “synesthesia” into a search engine. You could also read The Phenomenology of Synaesthesia by VS Ramachandran and EM Hubbard (April, 2003).