^I don't think I have pure synesthesia, it's more a mental association with colour psychology. An album might sound yellow or blue to me because of its general sound, because of its musical feeling, and because of its approximate pitch. Now, these three aspects should usually go well together if an artist has any sense of style. But it's more or less esoteric how one perceives these, and might be clouded by what we've got used to. For example that song discussed above (Kick In the Spleen) gives a dark blue vibe to me, maybe slightly violet, but definitely dark blue.
How is the synesthesia system even agreed on, is it the different wavelengths in sound as there are different wavelengths in different colours? For me it's just the mental image, feeling and psychology that springs to mind depending on the interval (soft or unstable), the sound used, the pitch, etc. We had this discussion years ago and someone said he could easily imagine Follow the Reaper sounding red, so I dropped it. I deem that album blue because it sounds cold, high pitch, with blissful melodies, midnight lakeside atmosphere, and it deals with bluesy emotions twisted with depression, alcohol, angst and so on. Maybe there's another level to this, but this is how my mind works. At times there could be a flash of dark red with a heavy guitar riff or whatever, but I don't see chords flying at me with different colours during the same musical piece. And just for a reminder, I don't see just colours, I see trees and lakes too.