What colour 什么颜色
有可选项,用which colour；没有可选项,最好还是用what colour.如：
What colour is Tom's favourite colour?汤姆最喜欢的颜色是什么（颜色）?
Which colour is Tom's favourite colour,red or blue?汤姆最喜欢哪种颜色,红色还是蓝色?