Red alert

The colours you wear can affect your mood and even improve your popularity.

Each fashion season, a colour plucked from an imaginary rainbow is crowned "the new black" - black being the king of colours, with a versatility bordering on the biblical. This autumn it is red. Whether you choose to wear red or not (I shan't) is a decision that should be based on personal preference and skin complexion.

What is most interesting about colours, however, is the psychology behind them. Red, for instance, is aggressive and brings out the masculine side of people. Some years ago a primary school in England that had hitherto had a red uniform and was painted red inside (I get a headache just thinking about this) had trouble with pupil aggression and lack of concentration. After calling in a colour psychologist, the board rebranded the school blue - a colour seen as in tellectual, and which has a calming effect. The pupils' behaviour changed dramatically. Pink is sometimes used in the cells of particularly disruptive prisoners; pink being a feminine colour, it, too, has the ability to soothe.

In the 1950s workers at a factory complained that their canteen was too cold. Even after the heating was turned up, they still complained, so the management painted the factory orange and, lo and behold, the workers thought they were warmer. The same thing happened when they complained that the black boxes they had to lift were too heavy. The boxes were repainted mint green; the load didn't change, but the workers were happy. Clearly there's more to colour than meets the eye.

Colour was particularly important to the Elizabethans, who dedicated entire books to its symbolism. Members of court would signal to each other by wearing green (meaning love and happiness) or turquoise (jealousy). Red was courage, black was grief: these were "popular" colours to be executed in.

Consciously or not, politicians use colour to great effect. Tony Blair often wears a red tie when he is addressing a Labour audience, when there may be Con servative voters he wears blue, and at times when he's feeling as if he is actually leading the country he wears purple - a fusion of red and blue. Historically, purple was reserved for royalty because it was a costly dye to manufacture: it took ten thousand molluscs to make one gram. At one time you could be tried for treason for wearing even a smidgen of it. Luckily those times have passed and purple hasn't been fashionable for a few seasons (watch out next year, though).

Our reaction to colour is primal. We associate green with fertile soil. On the whole, it is a comforting colour. But red spells danger and raises the blood pressure, though it is a long-wavelength colour, like orange and other "brights". These appeal to the more immature among us - think of what attracts little children - because, as we get older, we veer towards short-wavelength colours - that is to say, more sombre hues such as blues and browns. If you pick orange over blue (and most people over the age of ten do) it means you have a good heart but are a little shallow.

Although the little black dress is seen as the epitome of chic, black - which absorbs all colours - is actually worn by people who want to blend in and in fact feel a little insecure. Truly confident people wear white.