Answer:
What has roots that nobody sees, and is taller than trees. Up, up it goes, and yet it never grows.
What turns from red to black as soon as it touches water?
What is pronounced like one letter, written with three letters. And belongs to all animals?
The more of it there is, the less you see.
I can move even when you are still. I can be one or many.
Black we are and much admired. Many seek us if they are tired. We tire the horse, and comfort man, and turn White when we've fulfilled your plan.