What color is the number 7?

What color is the letter 'M'?  I don't mean what color is it on the screen.  I mean what color is the ideal, proto, conceptual letter 'M'? How about the number 7?  What does a musical fifth taste like?  I remember as a child, when I was memorizing the alphabet, that certain letters early in the alphabet were bright and colorful and full of daylight.  I, J and K were like trees in a jungle.  As I got past the middle of the alphabet the letters had more of a nighttime feeling; some blue, some black, some with stars.  Saying the alphabet aloud told a sort of visual story that helped me to remember.  By the time I got out to X, Y and Z, we were in outer space.  I didn't feel like I made up this visual story, it was just something I observed.  I can't remember the details now, just the impression... I guess I grew out of it.  I suppose that is the closest I'll ever come to experiencing synesthesia, a condition that connects senses like color and taste to letters, numbers or sounds.  It is a cross-sensory connection in the brain of synesthete.  It seems really interesting to me, but also a bit difficult and confusing.  I imagine when letters are colored differently than their inherent, synesthetic color, it must feel much the way that the Stroop Effect feels to the rest of us.
Take a look at these videos and tell me what colors you see.