what colour is it 是一个问句
what colour it is是一个从句,比如:I don't know what colour it is.这里充当宾语从句
what colour it is与 what colour is it 区别:
前者是陈述句形式,多用在从句中;后者是疑问句形式,多是单独的句子。
独立句子中,用what colour is it?
从句或间接引语中用what colour it is.
如:I like the bag. Do you know what colour it is?