WHICH ONE YOU ? 定係 WHICH ONE YOU?

It depends on what you want to ask, here are some examples,

Q-Which one do you like?
A-I like the blue one.
(Choose one from the group, ask for your preference)

Q-Which one are you looking at?
A-I am looking at the one on the left.
(If you are using 'are', then you have to add 'ing' on the verb)

Q-Which one is it?
A-It is the green one.
(If you want to ask which car is yours, then you use 'is' as there is only one item. The green one is mine.)

Q-Which one are yours?
A-The blue one belongs to me.
(If you want to ask which one is yours, then you use 'are' with 'yours' at the end.)

*** HOPE IT HELPS ^>^ ***

Which one are you.

example: Which one is right?

Who are you or Who you?

of course, it is which one are you, it just didn't make sense when you said which one you!

Which one are you?
"Are" 係動詞, 唔可以無咗.