White propaganda is correctly attributed to the sponsor and the source is truthfully identified. (The government, Voice of America, for example, broadcasts white propaganda.)
Grey propaganda, on the other hand, is un-attributed to the sponsor and conceals the real source of the propaganda. The objective of grey propaganda is to advance viewpoints that are in the interest of the originator but that would be more acceptable to target audiences than official statements. The reasoning is that propaganda materials from an identified propaganda agency might convince few, but the same ideas presented by seemingly neutral outlets would be more persuasive.
Un-attributed publications, such as articles in newspapers written by a disguised source, are part of grey propaganda. Other tactics involve wide dissemination of ideas put forth by others—by foreign governments, by national and international media outlets, or by private groups, individuals, and institutions. Grey propaganda also includes material assistance provided to groups that put forth views deemed useful to the propagandist. This type is very common in news world. E.g. some people have expressed disliking on or, people have appreciated government move to ban opposition rallies on the roads etc.
Black propaganda also masks the sponsor's participation. But while grey propaganda is un-attributed, black propaganda is falsely attributed. Black propaganda is subversive and provocative; it is usually designed to appear to have originated from a hostile source, in order to cause that source embarrassment, to damage its
Prestige, to undermine its credibility, or to get it to take actions that it might not otherwise. Black propaganda is usually prepared by secret agents or an intelligence service because it would be damaging to the originating government if it were discovered. It routinely employs underground newspapers, forged documents, planted gossip or rumors, jokes, slogans, and visual symbols. For instance, a newspaper publishes a letter by a prominent politician to another asking for certain action. The letter may serve purpose of some interested group. The fact is that there has been no such letter ever existed. But damage has been done especially if it is done during election days.