Question

Iam black when you buy me red when you use me and gray when you throw me away

Answer 1

aint this a matchstick

Answer 2

The answer for the riddle I am black when you buy me red when you use me and grey when you throw me away is match stick.

Matchstick appears black at the top as the black portion contains sulphur to be burnt easily when will come in contact with fire.

It changes to red colour when it catches fire that means when we use it.

And after completely burnt it changes its state to Ash which is grey in colour.