How to add an avatar frame to a user group

.group-creators .post-avatar img {
 Bezel: 2px solid red;
}

What I want is that this avatar frame can be seen by all users, but only the creator user group can wear this avatar frame, and the effect you gave me code is to add an avatar frame for all users, but only the creator user group can see it
I want the effect that all users can see that the creators group is wearing an avatar frame, but the non-creators group is not wearing an avatar frame.