What is your favorite color of fall leaves?

Color and colour are both correct.
One is American English, the other is Brittain English.

The #631 's colour

The opposite of #631's color

Red

You can't spell fall without 'all'.

orange

Maple leaf red is my favorite but really it's the blend of different colors I like the most

What #2 said :D

Too bad, there's not gonna be a #631