Today is the 10th World Aids Day, which means that millions of people around the world should be reaching for their red ribbons - but what, asks a confused Jasper Pleydell-Bouverie, do all the other colours represent?

Over the past few weeks I've seen yellow, green, black, pink, scarlet, tartan, multicoloured, light blue and, of course, red ribbons pinned on to various lapels. Very colourful it all is, but it's also slightly unnerving. The wearer is, after all, communicating his or her political, social and possibly sexual leanings for all to see, and it's not always clear what the message is.

Take green, for example. You might assume that the wearer was a keen environmentalist, and green ribbons are indeed worn by green people. But they have also been worn by members of Sinn Fein, and, earlier this year, were stuck on the caps of professional golfers - in sympathy with a caddie with leukaemia. Imagine meeting someone wearing a green ribbon; do you talk about deforestation, decommissioning, or the final round at Muirfield in 1966?

I am not the only one to suffer such confusion. Red Ribbon International (RRI), which organises the Aids Awareness ribbon in the UK, is regularly asked for advice on ribbon identification. Apparently a lot of people, when they spot a new colour, think it's a different Aids cause. "We had a lot of trouble with black ribbons," says Mike Campling, director of RRI. "Many people thought that it was something to do with black people and Aids."

RRI run an unofficial ribbon advisory service. They have an office list, regularly updated, of all the ribbon campaigns of which they are aware. Black, Mike Campling was able to tell me, has been used by Oxfam in a Rwanda fundraising campaign, but it was also used by Anti-Eta campaigners in Spain last July. And then it was used at the funeral of the Princess of Wales.

In Scotland, thanks to Waverley Care in Edinburgh, the Aids awareness ribbon is tartan, and the Stonewall Group have their own rainbow ribbon in the colours of the gay flag to support gay and lesbian rights. Dark blue is worn for "ME awareness" in Britain and "total freedom on the Internet" in the US. Mauve is for animal rights. Yellow is for "I want someone home" - usually a political hostage or a prisoner of war, but most recently Louise Woodward. And pale blue could mean that the wearer was a supporter of the anti-drink-drive campaign or the Coventry Community Safety Team 1996, whatever that may be.

Is it just me who's ignorant - or do most people not know what these "other ribbons" refer to? When were we told? The original Aids ribbon was launched at the Toni Awards ceremony in New York in 1991, but I get the impression that some of these others were dreamt up at village hall meetings - possibly in cahoots with a local haberdasher's. (Apparently orange ribbon hasn't been selling too well recently. Perhaps we should expect a campaign. Ulstermen? Sun-worshippers? Friends of the man from Del Monte?)

Strange though it may seem - given the simplicity of the ribbon concept - there are companies that will supply tied ribbons specifically for your campaign. I rang one, called Alan Salter, which supplies pink ribbons to breast cancer charities, and got the impression that the company was buoyant on the tide of ribbon mania. Yes, a spokeswoman told me, they were answering increasing numbers of enquiries about ribbon, and next year I could expect multicoloured ribbon campaigns, and ribbons with logos printed through them. "We could do you any colour you like," she added hopefully. "If your paper wants to launch a campaign for something, then we could supply the ribbons. You could, say, have 200 limited-edition ribbons and sell them for pounds 5 each."

Clearly, the original idea of ribbon-wearing - intended as easy, simple and cheap - is undergoing prostitution, but is this having any effect on the red ribbon campaign? Happily not, according to Mike Campling. Most people know what the red ribbon stands for, and far more red ribbons have been distributed than any other colour - 6 million every year compared with about 500,000 of all other colours put together. In total more than 100 million have been distributed world-wide and this year they are being worn for the first time in countries as far-flung as Ecuador, Senegal, Bangladesh, Sri Lanka, Cambodia and the Philippines.

All being well, such initiatives should prevent the Aids awareness ribbon being overwhelmed in the confusion that surrounds its imitators. Benetton's new advertising campaign, launched today, will help. It shows the newest addition to their Undercolors range, knickers featuring the red ribbon.

It is already one of the most widely understood symbols in the world; we can only hope that, for the sake of world health, the red ribbon becomes even more widely known. Thanks to WH Smith, this week there will be no excuse not to wear one; they will be displaying collection boxes and red ribbons in 400 stores to raise much needed funds for the National Aids Trust. The fight, after all, goes on.