Here is a review and clarification of what this topic actually entails, separating the slang from the art.
Modern audiences watching these films today are often shocked by the innocence of the "blue" content. Compared to global streaming standards, these films are tame; they rely on ghoonghat (veil) pulls, kajal smudging, and throbbing thumri songs. The "nudity" is usually a body double or a clever shadow. Desi Hindi Blue Film