Frequent travelers always know when they’ve reached Colorado. First, there’s the lack of oxygen. Then, there’s the fashion.

Flannel. Camo. And puffer vests.

While Colorado is far from being a runway capital and lags the nation’s coasts in parading the latest apparel, it has developed a distinct style, experts say. Think famously rugged, active outdoors and western heritage. Pair that with contemporary embellishments.

Women’s flannel shirts tend to be available everywhere — from big box stores to chic boutiques. At the latter, they range from traditional to trendy, flaunting bright colors, floral embroideries and larger check patterns.

“Colorado is an outdoor state well-known for adventures, which lends itself to a laid-back style,” says Amie Bennight, owner of Eve’s Revolution in Colorado Springs and co-owner of Delilah’s, a sister business that operates a fashion truck.

“Mountain chic” is how Carrie Hibbard, co-owner of Terra Verde Boutique in the Springs, describes the look. “Casual but styled at the same time.”

So the wearer can hike, work at the office and go out with friends — all while sporting the same outfit. If dinner or a drink is included, common advice from Terra Verde style consultants is to “throw a jean jacket over it,” Hibbard says.

A jacket delivers not only a layer of fashion but also a layer of clothing, which can prove particularly useful in a state where winter temperatures sometimes drag into May.

“Everyone has this perception of what you might come across in Colorado, and it’s different from California, Florida, Georgia or New York,” Bennight says.

This year, the fashionista stars have lined up in the shape of Colorado; many of the elements that create the state’s signature look are what’s “in.”

Since the fashion wheel turned back to high-waisted and wider-legged pants about three years ago, denim once again is all the rage, Hibbard says.

And it comes in a variety of styles. Skinny jeans are “out” now, replaced by options including straight-legged, flared bottom a la the 1960s and 1970s, wide and extra wide. And then there’s the bowed barrel-style leg that’s XX-wide and offered in boho designs such as patchwork and bandana.

Deconstructed rips or tears continue in some lines. And the “raw” look — cut-off rather than seamed hems — is on point and handy because jeans that are too long can be fixed with a pair of scissors, Bennight says.

The Colorado look extends beyond jeans into straw and felt hats, along with dresses featuring country designs that can be worn with cute cowgirl boots.

Stripes and polka dots add excitement to spring’s lighter and brighter colors in tops of all kinds, including soft knit sweaters, according to Julie Megahan, co-owner of Delilah’s.

“It’s a great transitional piece for Colorado — you won’t get too hot, but you’re covered — and one you can wear with denim or other fabrics,” she says.

One-piece rompers and overalls have maintained en vogue status due to their comfort and out-of-the-ordinary presentation, while camo-patterned clothes have faded away. Also passe: tunics atop leggings.

But you’ll still see those pieces because in Colorado, where most women dress up only occasionally, “to each her own” is the overarching theme.

As Bennight says, “We all want to find something that makes us feel special and unique in a style.”