Answer:
Four fingers and a thumb, yet flesh and blood I have none. What am I?
What is black when you buy it, red when you use it, and gray when you throw it away?
I saw the dead bring forth the living. I saw the living bring forth the dead. What did I see?
I run cold and hot, I look blue but am red. What am I?
If a man carried my burden, he would break his back. I am not big but leave silver in my tracks. What am I?
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.