I have experienced synesthesia for about 20 years now. It specifically affects me with regard to sound, and even more specifically with regard to music. For some reason, certain audible tones or noises are associated with colors in my mind--I can almost "see" the sounds.
And it gets even more intense when I'm listening to music, which is why I prefer to listen to the work of bands and artists who perhaps put as much or more emphasis on timbres and textures than, say, lyrics or songwriting. Those are secondary concerns in my mind, because where they might "paint pictures" in others' imaginations, in mine, the actual SOUNDS themselves create shapes and colors and form.
I could give some specific examples if they're wanted, but I think I probably sound like a pretentious weirdo as it is, so I'll leave well enough alone for the time being!