下面都是我自己的一些想法。

Which is your book? which是疑问代词作主语。
Which book is yours? which 是疑问代词作定语, book 是主语。
What colour is your car? what 是疑问代词作定语，colour是主语。
What is your car’s colour? what 是表语。

Whose book is this? whose为定语，book为表语。

改为宾语从句（用陈述句语气）

I don't know which is your book.

I don't know which book is yours.

I don't know what colour your car is.

I don't know what your car's color is.

I don't know whose book this is.

上述两块哪里有误呢？

 我觉得主要是疑问代词who,whom,what,which,whose及其中心词所做的成分搞不清导致的。