Gareth writes about the Perfect Pitch and tells a very nice analogy between a perfect pitch and color blindness:
There is a very good analogy to perfect pitch – that it is like seeing in colour instead of being colourblind – but it is still just an analogy. When you look at a picture and see a colour such as pink, can you tell me how you know it is pink and not, say, bright orange? No, you can’t. You just know. Similarly, I hear G and I hear that it has all the qualities of G-ness. That’s all. It doesn’t cause bright purple spots to float around that tell me it is a G.
I like this analogy very much. But head over and read the whole article at Dusk Puppy.