VATICAN diplomatic protocol is extensive and often leads to confusion. Nothing provokes more regular misunderstandings than the difference between a "state" visit to the Vatican and a "private audience" with the Pope.

Vatican "state" visits are limited in number and are carried out by heads of state, usually returning one of Pope John Paul II's many overseas pastoral visits. Such state visits are not only long on ceremony (they can last up to five hours) but they also imply that the visiting head of state, out of respect for the Vatican, will come to Rome only for that purpose.

Such was the case when President Patrick Hillery made a state visit to Pope John Paul II in 1989. President Hillery also made a state visit to Italy that year but was careful not to run the two together.

President Robinson's audience in the Vatican was, however, "private". It is routine practice for heads of government or of state, while visiting Rome, to ask for a "private" audience with the Pope.

Cuban President Fidel Castro and Israeli Prime Minister Benjamin Netanyahu are just two examples of leaders who "added on" a Vatican visit while in Rome for other reasons, doing so with out in any way offending the Vatican.

Dress code for Vatican audiences has traditionally implied black or dark clothes, with many women still choosing to wear a black veil or mantilla (Mrs Kwasniewski, wife of the Polish President, Mr Aleksandr Kwasniewski, wore one during an audience last week).

Not all women wear veils, while one or two have chosen not to wear dark clothes. Perhaps the most celebrated example was Raisa Gorbachev, wife of the former Soviet president, who wore red during a historic 1989 visit.

On the question of any alleged offence given by the sombre green worn by President Robinson, a Vatican senior spokesman, Dr Joaquin Navarro Vals, who was present for the visit, absolutely rejected any suggestion of offence given or taken when asked by The Irish Times.

Had any form of offence been perceived by the Vatican, it is almost unlikely that the next day's Vatican daily, Osservatore Romano, would have carried a front page picture of President Robinson with the Pope in the Apostolic Library.

As for mimosa, it is traditionally given by Italian husbands, boyfriends and sons to their womenfolk on March 8th to mark Women's Day, with some women opting to wear a sprig in their coat lapel.