I don't know. The Harold McGee book might have it.
I do notice that the color intensifies during the boiling and then peaks, and then if you leave it in too long, it starts to fade and kind of go grey. I don't know if it's matter of taking it out at the right moment or if the ice actually helps the color. It definitely helps prevent mushiness. The veg should be completely cold to the touch before you take it out of the ice bath.