Why would you need to change it?
It is not used when a user registers on the site and question and answer is required the fields are blank and the user must create their own question and answer. It is used when an admin user creates a new user but the admins can easily type something else in there we are just saving him some time. The main purpose for it is to be obvious what the answer is in the case where the user did not provide the question and answer themselves otherwise the user will not know the answer and will not be able to recover their password. It comes from a resource file so it can be localized for different languages but I don't see any reason why it would need to be customizable since you can set it to whatever you want when you create a user and the default question and answer serve their purpose for the case where the user did not create them and needs to be able to know what the answer is to the question, it is obvious what the answer is for the question "What color is blue?" It is only used in those cases where the user does not end up creating the question and answer themselves and the user can change it at any time on their user profile.