Yesterday I was experimenting with this.. I sat down at my piano and would try to see colors corresponding to my notes. At first not much was happening, but after a while I just imagined it and I could start to associate the sounds with colors. Lower notes were darker tones.. crimsons.. navy blue.. down to near black.. higher notes were lighter tones.. beige, pink, then going down to brighter reds, greens and blues. I thought this was kind of interesting so I played the song fur elise, and In my mind I created a picture with the colors I was hearing in the song. Wherever I was, I would imagine the matching tones being filled in in the picture. For example, during the 3rd section in fur elise, I was watching the lake being painted in my mind. I noticed that, if anything, I was playing much better. For me, the painting of fur elise is a man and woman standing in front of a lake, there's grass and trees all around and a cottage behind. The woman (Elise, I guess) is wearing a big red dress and has a painful expression on her face. Interesting, because it all came from nowhere!
Also, later on while on a run I would try to imagine the sounds of various things around me, and create a song from the landscape. It worked kind of well although it only used 4 or 5 sounds.. but I liked it.
Now, the whole reason that I'm trying to do this in the first place is because of the memory aspect that people with synesthesia seem to have. In short, it looks as if it's a means to turn abstract data like words or sounds into something meaningful.. increasing retention and recall almost subconsciously.
I haven't really noticed any difference yet, except that I was starting on German in the evening.. I browsed a few introductory words, there were 3 or 4 that I didn't know. I forgot most of them only 5 or 10 minutes after that, but when I woke up a few hours ago, for whatever reason I managed to remember them all, even though I couldn't before.
Even if it had no useful application such as that, I still noticed that it makes music much more deep and enjoyable.
Does anyone have any experiences with synesthesia? I'm really interested in this
I was reading a book once and a character described an experience as 'sounding sort of like the color blue tastes', and i immediately got this bright, metalic sort of taste in my mouth, and then it went right to a high pitched note, kind of like pinging a crystal glass. Then i thought, 'that's wierd, blue should sound softer than that, more like a flute arpegio. But, then again, if blue has that metalic taste that i got, then that TASTE would sound like the high note, even though the color doesn't sound that way.' then i put the book down because i was getting wierd thoughts 
