If I want to give a negative reply for a which-question, such as, which one is your favourite ? Can I merely use a word "None" to reply to the question?
None is short for "not one" and is used mostly with countable things. Like, for the question, "How many books have you read?", you can answer "Not one" or simply "None".
While just saying a single word like "none" as an answer will express the same meaning, it is usually encouraged to speak in a full sentence like, "I have read none", at least in more formal conversations.
For the question you asked, since the options that you would have are countable, you may use "none". However, if you are specifically given options to choose from, you can also say, "None of these", to specify that you do not like any of the options that are given.
To learn more about the usage of "none", I encourage you to check out the following links: