Mary-Ann Sieghart: You can't be all things to all shoppers

At a time when we are resiling from bling, and conspicuous consumption, they offer sturdy value, unflashy goods

It's a funny thing, but Britain's most trusted and successful brands – Radio 4, the National Trust, John Lewis – are always questioning their appeal. Radio 4 is desperate for younger listeners, even though today's Radio 1 fans will be tomorrow's Archers addicts. The National Trust is frantic to break away from its tweedy image. And now John Lewis's head of marketing has complained that the chain is sometimes seen as too "beige".

He's right that beige is bad. Even the word is onomatopoeic. It makes you think of sludge and slacks and the stale smell of nursing homes. In fact, though, John Lewis isn't beige, it's taupe. Taupe is more contemporary but it still lacks personality. It's a playing-it-safe colour, widely used in hotels and in houses where the owners lack confidence in their own taste. You can't go wrong with taupe, but you can't go very right either. That could be John Lewis's motto. If you buy a sofa there or a duvet cover or a mug, it will never be naff. It will be reliably good quality and possibly quite tasteful. But it will never be quirky, fashionable, individual or remotely edgy. Just dependably inoffensive.

Maybe that's not a bad formula. After all, John Lewis is extraordinarily successful. It is regularly voted Britain's most popular retailer. In Management Today's list of most admired companies, it comes top for quality of goods and services. And just check out the numbers. John Lewis has sales of £750 per square foot of shop space, compared with £500-600 for Selfridges and M&S, £235 for Debenhams and just £190 for House of Fraser. It must be doing something very right.

Part of what it is doing right is questioning itself. For retail success is a constant process of self-improvement. John Lewis was definitively beige until about ten years ago. Then it revamped its shops and products, giving itself an upgrade to taupe. That was a start – it's now way ahead of the National Trust shops, which are still filled with twee floral designs that even many older shoppers find dated.

But, to keep up with its customers, it now needs a dose of flair and personality. For the demographics are moving against it. Time was when the onset of middle age was a liberation from the need to care about fashion or style. You just wanted a dress that suited you or a sofa that matched the curtains. In the 1970s and 1980s, everyone over 40 gravitated towards a uniform of slightly frumpy clothes that were nonetheless comfortable and well-made. Men just replaced their navy V-neck jumper for another when it frayed at the cuffs. Women did the same with their sensible skirts. And they went to shops like John Lewis and M&S to stock up.

Today's generation of middle-aged consumers couldn't be more different. If anything unites them it's the determination not to give in to that mindset. They want to remain contemporary and fashionable well into their forties, fifties and sixties. To stop trying would, they feel, be an admission of defeat, a surrender to the horrors of old age. They don't want to grow up to resemble their parents; they want to carry on looking like their children for as long as possible.

This is great news for high street fashion chains such as TopShop and Zara. You see women of my age and their teenage daughters trying on clothes in neighbouring cubicles (yes, I admit it) and comparing notes. For even if middle-aged women aren't aiming to look 19, they do at least want to be stylish.

What's more, we are increasingly internet-savvy. If we are in the mood for a new dress, we can browse individual retail sites or go to Stylecompare and tap in "tea dress" to see what's on offer on dozens of online outlets. If we want a sofa, we can check out Mydeco. So the competition for an individual John Lewis or M&S store is no longer local, the shops in that town centre, or regional, the shops in the nearest city. It's national and sometimes even international. You can order from Amazon's American site as easily as you can from its British one.

This has made life difficult for retailers like John Lewis and M&S. Both have relied on the 40-plus end of the market, where there used to be much more homogeneity of taste and much less competition. Both thrived in a world in which retailing was less niche and where shoppers were more interested in reliability and quality than style.

So how can you be all things to all men and women, as both these chains aspire to be, and not end up a dull shade of taupe? The answer is that you have to inject some flair and then differentiate much more within your store. At M&S, it's incredibly hard to navigate the shops. You have to fight your way through the shiny slacks and viscose blouses to locate something remotely fashionable. It's not clear what age group the Limited and Autograph ranges are aimed at. And who are the women who wear Per Una? Search me. The same problem afflicts the website. All the clothes are jumbled together. You want to be able to tell them your fashion age (which may be different from your chronological age) so that they can edit out the dowdy and the teenage for you. John Lewis is much better online.

These chains may be worried that if they introduce too much style or fashion, their loyal elderly shoppers will be put off. This won't happen as long as the basics – the navy V-neck jumpers or the plain white mugs – are still there and easy to find. And, importantly for both young-at-heart and older shoppers, as long as the ranges are kept well apart from each other. Neither wants to be tainted by the other.

Both businesses start from a fantastic base. At a time when we are resiling from bling, labels and conspicuous consumption, they offer sturdy, reasonable value, unflashy goods. In today's climate of insecurity, they seem reliable and trustworthy. When we are feeling alienated by bad service and rude staff, they offer kindly faces at the till, helpful advice and no-question returns. And as our suspicions of capitalism are mounting, John Lewis, at least, has a mutual structure which is seen as a model for both private and public sector. We love its values.

But that doesn't absolve them from the need to keep up with increasingly demanding customers. Smartphone ownership is growing by 70 per cent a year. We'll eventually want an app into which we can type "black jacket" and be given the location of every black jacket in John Lewis. We'll want to be able to scan the ticket of a bulky item with our phone and have it automatically delivered to our home and the receipt emailed to us, without having to queue at the till and fill in forms.

And if my generation is demanding, what about the one below? My daughters wouldn't dream of shopping at either John Lewis or M&S. They may grow to do so, like Radio 1 listeners migrating to Radio 4. But it's not a given. So it's good that both John Lewis and the new head of M&S, Marc Bolland, aren't complacent. They know they have to move on from taupe. For it isn't the future. It's barely even the present.