What matters, ultimately, is not just the thing itself but the context in which it is used and presented. If I announce that "picture present" means "no" and "picture removed" means "yes", the presence or removal of the picture still acts as a communication system and its use is likely considered a form of communication by the law.
However what makes canaries special is that mere removal or absence is ambiguous in that it can be unintentional. The question then is whether this is more akin to changing your response from "No" to "No comment" and whether this change itself when you have previously announced you will always answer "No" as long as it is truthful already indicates "Yes" (thus violating the gag order).