Before joining The Globe and Mail as a business writer in 2010, I worked for two Canadian investment banks. In those years leading up to, and during, the financial crisis, Bay Street abided by unwritten rules of office dressing that stressed conformity. Showing off individual style often earned you a talking-to from someone senior, or chides from colleagues, who would call you a dandy.

That dress code dated back decades, and its few exceptions required lavish spending. Custom-made or Canali suits were acceptable; pastel J.Crew ties were not. As for accessories, there were few available options. Cuff links could be worn – but they were really only an option for senior people such as managing directors and partners.

Not even a decade later – and five years too late for me – Bay Street’s style guide has become noticeably less restrictive. The rulebook hasn’t been completely rewritten, but professionals, from bankers to lawyers to consultants, are finally free to show some flair.

Millennials, who like to challenge convention, are partly to thank. Take Jonathan Tarshis Neil, a 31-year-old vice-president in private equity at TorQuest Partners. On the second day of his first Bay Street job, he made the mistake of crossing an invisible style line. Fresh out of university and unsure of what qualified as acceptable office attire, the newly minted investment banker wore a light pink dress shirt to work. A concerned colleague was so fearful of the repercussions that he quietly explained this wasn’t just a sartorial slip-up but a major no-no.

Tarshis Neil didn’t see the logic in conforming. “If you’re going to wear a suit and tie everyday, you should get to wear what you want to wear, within reason,” he explains.

Though he toned down his shirt colours, Tarshis Neil continued to show a little something extra. He was the first banker I knew who freely wore turquoise-framed hipster-style glasses to work – and this was in 2008, long before they were mainstream. Eventually, his colleagues, and even some of his superiors, came to respect him for it.

Today, there are many more like him in high-profile positions. Growing up in a borderless world shaped by the Internet, millennials were taught by a steady stream of technological advancements that rules and habits can shift quickly. So it was with Bay Street style.

The two-piece suit is still the de facto uniform and navy blue will never go out of style. But in boardrooms now, you see everything from purple pocket squares to tie bars to monk-strap leather shoes. Beards, once thought to be unprofessional, are ubiquitous and some men even go sockless with shorter-hemmed pants. This season, navy suiting is giving way to lighter and more eye-catching chambray.

Of course, what passes as acceptable differs from profession to profession – and from firm to firm. Investment banks are arguably still the most married to the old fashion rules; management consultancies and law firms are typically more liberal; traders rarely bother to demonstrate much style, at least not at work, because they are largely tied to their desks; and investment advisers and money managers are known to show some flash, because they are, in some respects, their own bosses.

Across the board, the new approach to style has as much to do with the clientele of the new economy as it does the millennial workforce. Twenty years ago, the rigidly enforced dress code at places like IBM – with its drab suits, starchy shirts and wingtip shoes – set the tone among employees and the scores of professionals who advised the company. In part, the latter were upholding another unwritten rule: that you should dress like your client to show you share the same values.

But now, Apple, Facebook and Tesla have the juice, not to mention tech startups, which offer some of the most promising deal flow. That means professionals are increasingly faced with the prospect of pitching 20– and 30-somethings. It can be hard to connect to a recent University of Waterloo graduate in a hooded sweatshirt when you’re wearing a 3.5-inch-wide Hermès tie. That’s why fat neckwear, close-cropped haircuts, and button-down collars are being replaced by skinnier ties, edgier hair styles and shorter shirt collars that look best with simple knots, not double Windsors. These changes connote a fashion currency that matters to younger clients; in some ways, they serve as a secret handshake.

Such flourishes are discovered through many avenues. In the old economy, designers and tailors set trends. Now, the Internet and social media are equally influential arbiters of cool. “Before online shopping, and before the narcissism of Facebook and Instagram, you had to ask permission to have style,” says David Simmonds, a vice-president at McKesson Canada. In this new landscape, “we’re able to see ego in a way we couldn’t see it before,” he says – and that’s made calling attention to one’s clothing more acceptable.

Yet these flashes would never fly if senior Bay Street professionals weren’t also experiencing a change of heart.

Not long ago, being successful often meant killing yourself for the better of your client, and socializing involved consuming heavy amounts of alcohol. That way of life is dying as Street veterans become healthier. And being fit has made them more willing to don a form-fitting suit with attention-getting accents. In other words, they are learning to embrace style in their own way.

“Big, baggy fits were a way to hide ‘Molson muscles’ and love handles,” says Larry Rosen, head of Harry Rosen, reflecting on the days of ill-fitting suits and pleated pants. “We’re a more health-and-fitness-conscious society than we were before. Cripes, when I was a young lawyer on Bay Street, nobody worked out.” Now foodcourt restaurants such as iQ Food Co., famous for its healthier takeout boxes full of organic quinoa and shredded red cabbage, and Kupfert & Kim, which specializes in wheatless, meatless dishes, have the longest lines.

For all the progress, Bay Street still isn’t at the forefront of men’s fashion. Walk through Canary Wharf in London or La Défense, the new business district in Paris, and it is clear Toronto isn’t as cutting-edge. There, suits are so slim they look painted on, and super-skinny ties are de rigueur. Even relative to Montreal – where a bold business palette is much more common – Toronto is less willing to take style risks. “Fashion is a mirror of society,” says Simmonds, who travels frequently to Montreal for work. “If we hold that mirror up in Toronto, there’s definitely a haze of conservatism.”

But believe it or not, Bay Street is, in some ways, more progressive than Wall Street. Tarshis Neil did his MBA at Columbia and lived in New York City for a few years after, only recently moving back to Toronto. “There’s such a dress code there,” he explains – particularly for young professionals, whose default look is a Charles Tyrwhitt shirt with a Ferragamo tie and a dark suit. “People here,” he says, referring to Bay Street, “don’t have quite the same homogeneity.”

It shows in what sells. Holt Renfrew, which recently opened a men’s-only store on Bloor Street in Toronto, added a bottle-green suit to its lineup this spring and it sold far better than expected, says its men’s-wear director, Andrew Lepp. Even older men who are more resistant to the new trends have proven willing to experiment with colour in their own way, trying out eyeglasses with teal or cobalt-blue frames.

Yet everyone on Bay Street knows there are limits and that some boundaries are better not crossed. Even in my own head, the old-school rules still linger. When interviewing senior people in capital markets or corporate law, I make sure to wear a wider tie. If anything, it shows respect – and it puts them in their comfort zone, which helps them to open up.

The most experimental young professionals show similar restraint. “If we have a board meeting, and I’m the junior guy there,” Tarshis Neil explains, “I’m not going to take the opportunity to wear my most aggressive suit-and-tie combo.” That’s just bad for business.