询问颜色What colour is it? — 英语选择题

Mike有一支新钢笔。他先告诉Amy："My pen is not blue." Amy又问："Is it black?" Mike回答："No, it isn't." 最后Mike说："It is my favourite colour — green." 如果Lily没听见，也问Mike："What colour is it?" Mike应该怎样回答才正确？A. It is blue. B. It is black. C. It is green. D. It is a pen.