what's the colour of money?

Do you choose your shopping or does your shopping choose you? Meg Carter on the power of subliminal selling

can you smell a bargain at 10 paces? Do you have an eye for the best buy? If so, don't flatter yourself: there's more to it than good taste and discernment. Barclays Bank blue; the swirly lettering on a bottle of Johnson & Johnson's baby lotion; the smell of freshly mown grass in Sketchley's; background "hum" to break the deathly silence of the supermarket aisle. All of these are the hidden persuaders, part of an armoury of subliminal tactics now being used to encourage us to buy.

Proof of shops and manufacturers' growing interest in assailing our senses comes with the rush of British companies to register a selection of shapes, colours, smells and even sounds as trade marks following recent changes in the trade mark law. Furniture flavoured with a hint of cinnamon, beer- flavoured darts, rose scented tyres and even Cadbury's purple are now being considered by the Trademarks Registry. The reason? A belief that these subliminal features promise a serious competitive edge.

"Purple has been an integral part of our brand identity since 1915," says Cadbury's Richard Frost. "Certain colours signify types of confectionery product, such as green for mints and blue for biscuit," he explains. "But purple has royal connotations; it's a colour which has been seen as a symbol of quality for centuries."

Colour can be extremely persuasive, agrees Glen Tutsell, creative director of design consultancy Tutsells. "It also offers a clue to price. Deep, rich colours say 'I'm quality - a premium product'. Brighter colours: 'I'm better value or cheap and cheerful'." Colours increasingly act as a code for the consumer. Pale blue means cooling and soothing, white and stripy blue lines means low calorie, slimline. "It's a kind of shorthand," he says.

But colours have deeper properties, according to colour psychologist Angela Wright, who has advised companies including Ladbrokes and Vax. "People think colour is a matter of surface appeal. It's more. It tells us something. We know in the natural world not to eat a carrot that's green: it's the same principle."

Every colour has its own distinctive qualities and holds particular emotional appeal. One reason for the success of washing powder Radion is its packaging, Wright claims. At first glance, the choice of bright orange and blue seems madness - existing powders sell themselves on the promise of "washes whiter". But these colours convey "leadership, strength, uncompromising standards", she says.

"Heinz's use of turquoise for baked beans marked a departure from usual food colours - an autumnal tone with inherent properties of rich abundance and solid substance," Wright adds. In contrast, Texaco's black, red and white colour scheme conveys "efficiency, technological excellence and, to a certain extent, aggression". Meanwhile, Whiskas' "winter purple" appeals to the psychological mode of the cat owner: "A person who respects independence and single mindedness."

Packaging can also spin a myth: Johnson & Johnson's friendly, hand-written logo is a clear attempt to persuade us it's a small and traditional, family- run business instead of a major multinational. Meat, once presented in red spotted plastic film to convey bloody freshness, is now wrapped in clear film patterned with sprigs of parsley: to make it look more appetising to today's squeamish meat shopper.

But it's not just manufacturers who are manipulating our senses. "Branches of Rymans are split between an impulse buy area at the front of the shop, heavily red in orientation, including coloured lighting, and a back of store blue area for more considered purchases, such as computers and typewriters," says Nigel Oakes, head of the Institute of Behavioural Dynamics.

It's all to do with "environmental conditioning to reinforce the purchasing state", he says. And there's more to it than just colour. Many supermarkets suffer mid-week during the day when they are often empty. "This makes them an unpleasant environment to shop in - you feel more comfortable when there are other people around." So a number of major chains have recently introduced a background hum - "white noise" comprising unspecified sounds broadcast throughout the shop at between five and eight decibels to convince shoppers they are not alone. "At the very least, it masks the sound of the trolley wheels."

While you may be familiar with the smell of fresh-baked bread in your local Safeway or Tesco, have you thought why smells assail you at the entrance when the "bakery" is conveniently situated at the back of the shop? Because it encourages you to move through the aisles to the rear, passing other products on the way. And it works. Scent is the most powerful hidden persuader, stimulating immediate images from memory, able to inspire almost instantaneous evaluation of things, or people. Certain aromas evoke particular responses - peppermint and lily of the valley tend to make people more alert, vanilla and lavender are soothing. And they can be used to make us spend money.

In recent tests conducted by Chicago's Smell and Taste Treatment and Research Foundation, shoppers were found to be more likely to buy Nike trainers when they tried them on in a floral-scented room, even when the price was then raised. Latest converts to the power of smell include BT, which has considered the potential of scenting its public phone boxes to mask unpleasant smells. Dry cleaning chain Sketchley recently introduced the odour of fresh cut grass and grapefruit in branches to conceal the smell of dry cleaning chemicals. "Of all the senses, smell is the one most closely linked to memory - a bad smell lingers," Sketchley marketing director Nick Joslin explains.

At Christmas, Woolies perfumed a number of its stores with fruit punch, literally dousing shoppers with festive spirit. At least one high street travel agent is testing the smell of coconut oil. An estate agent in the North East recently tried vanilla fragrance in the hope it would ease anxiety to encourage prospective housebuyers. A legal practice which recently moved from old to modern premises is using the smell of leather furniture "to reinforce the idea that they are an established, reputable firm", an employee confides. And luxury car salesrooms have long employed the same technique.

The reaction of the humble shopper to all of this is hard to gauge. On the one hand, Nineties consumers are past-masters at deconstructing marketing and advertising messages. On the other, they are sceptical consumers, ever watchful for the unethical or misleading claim.

Most feel there's something unsavoury about subliminal tactics. When a number of US companies tested subliminal advertising, Coca-Cola tried one commercial involving split-second images of the word "THIRSTY". Not only were the results inconclusive, but consumers were put off by the covert manipulation. Oakes describes titillating and targeting consumer's senses as "subrational" rather than "subliminal": "Subliminal means below the threshold for detection. If that were the case, it wouldn't work." Tackling one sense in isolation is unlikely to result in increased sales. "But producing the right ambience undoubtedly has results."

Yet Oakes remains cautious. "It's more than a gimmick: it's being driven by companies trying to increase profits. But they would be foolish to believe they can rely on tactics like these to guarantee success. After all, these tricks are mainly cosmetic. And they're tantamount to manipulating the customer, which is largely unethical." Instead, he advocates: "The creation of an environment conducive to selling. You need only a few people to start talking about 'trickery' and you've lost all credibility." Even so, he concedes, there is a fine line to tread between "encouragement" and "persuasion".

Wright remains convinced that subliminal influencers do have an effect, and that too few companies fully consider the psychological implications of the tactics they employ: "People just don't realise the inherent stress factors associated with vibrant and garish tones." Consumers may well feel manipulated if they realised how they are being targeted, she admits. "But I believe I'm trying to address strident discord in the world around us - to create a more harmonious environment which isn't stressful. It's more than manipulation." It's for the greater good. But whose?