Can you complete this riddle?
{"name":"Can you complete this riddle?", "url":"https://www.quiz-maker.com/QPREVIEW","txt":"What is black when you buy it, red when you use it, and grey when you throw it away?, What is it that when you take away the whole, you still have some left over?","img":"https://www.quiz-maker.com/3012/images/ogquiz.png"}