I am black when you get me,red when you use me,and white when you're all through with me.What am I动动脑筋啦

I am black when you get me,red when you use me,and white when you're all through with me.What am I动动脑筋啦
I am black when you get me,red when you use me,and white when you're all through with me.What am I
动动脑筋啦

I am black when you get me,red when you use me,and white when you're all through with me.What am I动动脑筋啦
charcoal
木炭

coal?不很肯定，好像是什么跟火烧有关的东西

charcoal
木炭