Is this the colour of the new millennium?

Peter Popham argues that Pepsi's blue period may inadvertently have captured the mood of melancholic times

Joni Mitchell's best record; Derek Jarman's most haunting film; the canvases of Yves Klein, Joan Miro, Rene Magritte and Henri Matisse: blue is the thread that links them all. "Blue", Matisse remarked, "acts on feeling like the strong blow of a gong." Now Pepsi, in the advertising campaign launched yesterday, is paying pounds 300m to make the colour its own.

It is a bold, perhaps a desperate gamble. Pepsi, after all, is not turning blue, does not have a new, blue ingredient (extract of sea water, perhaps?). In fact, it is proud to declare itself unchanged in every detail - except the colour of the can. Last week Pepsi was red, white and blue - like just about every other cola on the market - with red predominating. Today it is blue, blue and blue, with a smidgen of red and white for old time's sake. And therein, Pepsi hopes and prays, lies the magic ingredient that separates disaster from triumph.

It is an insanely extravagant nonsense, a pounds 300m insult to the public's intelligence. Yet something tells one that they may be on to something. If this is crassness, it is crassness on such a cosmic scale that it cannot fail to command our attention, however briefly.

To understand Pepsi's strategy, one must appreciate that we are on the cusp of the new millennium. We are also, according to some enthusiasts, into the Age of Aquarius, which began six weeks ago when Uranus moved into Aquarius (more serious astrologers say that's all baloney). In the marketing gobbledegook with which Pepsi explained its campaign, the organisation stated: "The new identity effectively leverages blue as Pepsi's signature colour and clearly communicates Pepsi's young, fun personality into the year 2000 and beyond ... the blue grid pattern gives the identity depth and dimension - projects the brand into the next millennium, leaving its competitors stuck in the 1800s and 1900s."

The thing about colours is that they contain a multiplicity of unrelated and even contradictory messages. The "young, fun" message of Pepsi's desideratum connects with blue's primary dictionary definition, "of the colour of the sky and the deep sea", awakening thoughts of summer holidays and warm seas. It perhaps even revives memories of the "Club Pepsi Max" promotion, when Pepsi took over Ibiza's Club Med, sprinkled it with stars and celebrities, and sent their competition winners there.

But "fun" is the label on only one of the boxes in which blue keeps its meanings. "... The colour of smoke," the OED goes on, "vapour, distant hills, steel, thin milk ... said of the veins as they show through the skin ... often taken as the colour of constancy and unchangingness." In Britain, it is the colour of the Tories. But elsewhere, too, it has strong associations with conservatism, seriousness, chilly formality: the qualities that made The Big Blue such a fitting epithet for IBM in its glory days, before the fruiting of that tiresome little Apple.

Pepsi may be content to buy into some of these messages: seriousness and formality, for example, may be the opposite of youth and fun, but they are not inappropriate signals for a company as aged as Pepsi to transmit. But can Pepsi be equally phlegmatic about having the product linked to "the blues", to "blue funk" (defined as "extreme nervousness, tremulous dread"), to the emaciated melancholy of the down-and-outs that Picasso painted compulsively in his Blue Period, to blue as a metaphor for blindness and mortality in Derek Jarman's film Blue? Can the company sleep altogether easy knowing that Pepsi is at one with "the colour of plagues and things hurtful"?

The fortunes of blue have changed over the centuries, broadly following shifts in the price of the pigment. Thus, when first employed by European artists in the late 12th and early 13th centuries, it could be obtained only by grinding the semi-precious stone lapis lazuli, and was hugely expensive: the more blue in a painting, the richer and more pious the client. So blue came to be used invariably for the clothes of the Virgin Mary.

By Picasso's time, however, blue had become the cheapest colour, and one explanation for the Blue Period was that this was the colour he could best afford in those dog days. Blue was the colour of the struggling painter, just as the blues became the music of the struggling black musician.

In between these two dates, however, came blue's apotheosis, when it was adopted as the defining colour of Calvinists and other Protestants in their struggle against the forces of the papacy, whose symbolic colour had always been red. Here, in the confrontations of post-Reformation Europe, we have the closest prefiguring of today's cola wars: and it is appropriate that now, too, the challenger, the outsider, the pretender to the crown, should be the one to adopt the colour blue. Blue as the colour of the anti-Catholics fed into such characteristic products of Protestant culture as the blue-stockings, and the blue jeans and blue collars, which became the uniform of the Protestant work ethic.

For the marketing guru Wally Olins of Wolff Olins, the cola war between products that are virtually indistinguishable and have "no intrinsic merit" is inevitably a matter of awakening emotions and harnessing fantasies. "Coca-Cola with its red colour completely dominates the generic," he says, "and everyone else who competes with them ends up going for red, too - like Virgin, for example. What Pepsi are trying to do is to break the generic, to make people see fizzy drinks in a completely new way."

But identification with a colour - and specifically with the colour blue - is clearly in the air. With somewhat creepy prescience, the avant-garde fashion magazine Don't Tell It devoted its March/April issue to the theme of blue, claiming it as the pre-eminent colour of the 20th century. "Blue captures so much of the ambivalence of today," the editor, Jiro Ejaife, enthuses. "Something triggers the sense that this is the colour of now."

Sea and sky, conservatism and the work ethic, plague and melancholy ... perhaps Pepsi's marketeers really have tuned in to some deep message in the Zeitgeist. Though I strongly doubt that it's enough to make me risk rotting my teeth.