Set to be one of the key colours of the coming season, we show you how to wear it well .

If blue is the ideal colour to wear in high summer, then grey makes perfect sense as the days shorten and the mercury starts to fall. It’s long been a vital hue in any well-dressed man’s wardrobe – just take a look at archive shots of Mr Gary Cooper, one of the best-dressed actors of all time, if you need any persuading – but, worn well, it can also have a contemporary, urban edge. It looks right in the city (perhaps it’s all that concrete), and just as good on dull, cloudy days as it does on bright, sunny ones.

In the AW15 collections there are, if not 50, rather many different shades of grey, particularly from brands such as Brunello Cucinelli, Bottega Veneta and Acne Studios. Where to start, then? There’s a world of difference between the classic garments that inspired the novel The Man in the Gray Flannel Suit, which was Mr Sloan Wilson’s treatise on post-war conformity, and the way that contemporary designers use the colour. In fact, the world’s leading style pundits have been taking grey and making it, well, rather fun. For an up-to-the-minute user’s guide we turned to the streets of London, Paris and Milan for inspiration. Read on to find out how it’s done.

Mr Simone Marchetti, the fashion editor of Italian newspaper La Repubblica’s weekly style magazine, looks delighted here in his grey ensemble, and rightly so – he’s happily selected three elements of classic menswear and put them together in a fresh and disarmingly casual way. It would be hard to imagine how a man wearing a double-breasted suit and double-breasted overcoat could look relaxed, but the soft blue sweater – crucially worn without a shirt – and the lightweight fabrics convey a modern, carefree attitude. While the two greys are almost identical, it’s instructive to see how different they look on account of the contrast in texture between the suit fabric and the fuzzy overcoat. Of course, the fact that the suit jacket is unbuttoned and the overcoat draped around the shoulders, also affects the dégagé impression this outfit makes on the observer.

Grey creates a flat, neutral background so it works really well as a grounding for vibrant pops of pattern and colour. In this case, Thom Browne’s signature tri-colour grosgrain peeks out from beneath the jacket’s cuffs and it’s matched by the colours of the scarf. The pale shade of grey (which is one that Mr Browne himself frequently wears) works perfectly with a white shirt, which lends it a severe, minimal look that’s highly suitable for the office. The quilted gilet, meanwhile, adds a subtle note of Italian influence. And although we know better than to describe the appeal of a classic, gold watch (is that a crocodile skin strap?) as timeless, we do note that it gives the outfit a welcome touch of gravitas and class.

The Italian fashion insider Mr Alessandro Squarzi (he’s an agent for an armful of different labels) frequently catches the attention of the street-style photographers, and for good reason. On what looks like a cold day, he’s captured in an outfit that exudes sprezzatura, which is a quality much more frequently discussed than it is seen. The cotton chinos match the white shirt, which contrast well with the three layers of grey wool that take the form of a dark cardigan, a soft jacket with eye-catching white buttons, and an overcoat that seems to possess a certain martial swagger. Note how the differing shades of grey add a richness and three-dimensional quality to what is sometimes considered a rather flat colour. The overall impression is casual and confident, smart enough for coffee with a client, but comfortable enough for a day spent charging around town.

As grey is a rather subdued colour, it can be a good counterpart for dense patterns, as seen in this photograph. Here a raglan-sleeve flannel overcoat drapes almost like a gown over the unusual blue and white jacket, which has a shawl collar and attention-grabbing ribbon fastening. The bottom layer is an op-art inspired shirt that brings to mind the work of Ms Bridget Riley, but central to the way it fits into the outfit is the low contrast that exists between the black and white shirt, the blue and white jacket and the grey overcoat.

Before mountaineers influenced us to wear goose-down jackets, men relied on substantial wool coats to keep out the winter chills. This subject is looking back to the elegant, pre-goose down era, while dressing in a way that’s entirely contemporary thanks to the slim cut of his heavy coat. In fact, he’s sporting more wool than the average sheep because apart from the cotton shirt everything is woollen – the tie, the waistcoat, the single-breasted blazer and the structured overcoat. However, at every turn there are details that update these traditional elements – there’s the slim tie clip, the nautical buttons on the blazer and the overcoat’s flapped breast pocket and astrakhan collar.

The appeal of grey goes beyond suits and jackets. This modern-looking man changes his mood with a pair of black pleated trousers, which have a certain intensity thanks to the contrast between their colour and the pale overcoat and sweater. The loose-fitting polo-neck looks thick enough to keep him warm in the coldest weather, while the overcoat is simultaneously timeless and elegant. He looks as if he might be off to have drinks with the Irish playwright Mr Samuel Beckett in a Left Bank café, or to edit a highbrow (if low-circulation) literary magazine. These are worthy sources of sartorial inspiration, although we wish he’d keep his mind on that expensive looking leather bag – someone will have it if he’s not careful.

None of the people featured in this story is associated with or endorses MR PORTER or the products shown