My daughter Emma and I went for an autumn walk last weekend. It’s peak time for checking out all the colors of the fall leaves, or “leaf peeping” as it’s called in areas where tourism is built around fall.Emma picked up a rainbow of red, orange and yellow leaves and asked me a simple question. “Why do leaves change their color in fall?”Hard as it is to confess, I had no idea. But in searching for some answers, I found that lots of folks shared my confusion about this great mystery of fall.It turns out that three factors influence autumn leaf color: length of night, weather and leaf pigments.