Antonyms for "gave green light" would be phrases indicating not allowing or prohibiting actions. Some examples include "put a stop to," "said no," "rejected," "banned," "forbid," "vetoed," "disapproved," and "blocked." These phrases indicate that an action or decision was not approved or authorized, and may reflect a lack of agreement, authority, or permission. Antonyms can be useful for expressing a range of ideas and perspectives, and can help to clarify the meaning and tone of a sentence or statement. Whether used in conversation, writing, or other forms of communication, antonyms can offer a valuable tool for expressing contrast and opposition.