Why we get fall color(or not)

 What's up with these trees( and some shrubs) in the fall?  I seem to have gotten this question a lot in the last few weeks, so here goes:
Both chlorophyll(green) and carotenoids( yellow,gold, brown) are present in the chloroplasts of leaf cells throughout the growing season. Most anthocyanins(red/purple) are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.
During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.
Why is the color of some trees ( expecially maple and liquidamber) not the same from year to year?
A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out. These conditions-lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.