What/Which color do you like?

兩者皆可
If you use which, you need to give them choices, for example, Which color do you like, red or blue?

I think so.

you could use either
Which colour would you prefer? Red or blue? (with choices)
or..
What colour do you like/? (with no limit)

What/Which color do you like?
如果兩者都可以

Which colour do you like? - 你提供顏色給答問題的人選擇o

hat colour do you like? 沒有提供頻色給對方選擇o

2013-01-10 16:11:46 補充：
What colour ........ 代替 hatｃｏｌｏｕｒ．．．．．

what ,其實看情況
用WHAT 是問你喜歡什麼顏色
不用在特定情況也可以問,
而WHICH是要在有選擇的情況下用
例如你看見有兩種顏色或以上時,才問別人你喜歡哪一種顏色(which color do you like?)