I suspect that synaesthesia isn't all that exotic, and most people experience mild forms of it. I for one remember associating letters with colours when I was younger, though the colours were different (A,E and M were red, B was green, C and G were orange-yellow, and H was either red or blue). Some years later, I developed the theory that the mapping came from a set of alphabet blocks I played with when I was an infant.
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