Why does frozen skin darken?!

Freezing kills the skin cells, and the blood supply goes away.

First it turns WHITE, then it goes dark as it start to rot.

Cuz we are filled with blood:. It's might be 2nd degree frost bite which is
the skin may freeze and harden, but the deep tissues are not affected and remain soft and normal. Second degree injury usually blisters 1–2 days after becoming frozen. The blisters may become hard and blackened, but usually appear worse than they are. Most of the injuries heal in one month but the area may become permanently insensitive to both heat and cold. The deep frostbite results in areas of purplish blisters which turn black and which are generally blood-filled. Nerve damage in the area can result in a loss of feeling.