What causes the variety of autumn leaf colors?

This site gives a very thorough explanation of the compounds behind each color and their functions in the plant (a bit too complex to reproduce here)

The colors in the leaves change due to the slowing of sugar production in the trees. Sugar production is fine in the spring/summer and when it slows in the fall-we end up with bright reds, oranges, and yellows on our trees.

Autumn Flower:

Now, petal, fall.
So sad to be the only one:
Your sisters all
have said goodbye to Summer’s sun.
Now hear their call:
Drop softly down as they have done.

And, green stem, fade.
Wither, and bow your tired head down.
You were not made
to last. No, let your lush life drown
in Death’s parade
of orange, red, and gold and brown.

Yes, flower, die.
And no more smile your face upon
this weeping sky;
But smile at us when you are gone.
And do not sigh
for beauty. Yours goes on and on.