These are the people who decide what you'll wear

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Denim is making a comeback, but maxi dresses are losing steam. And the red wine-inspired marsala color is the hottest hue of this year, but 2014 was all about radiant orchid purple?

Keeping track of the latest styles can be dizzying enough. But for a select few, the work doesn't start there. Instead, for the fashion industry's trend forecasters and color experts, it's all about predicting the big themes that will appear on each season's runway—and what will eventually end up in consumers' closets.

How international relations affect your wardrobe

Trend forecasting firm WGSN begins the process of identifying key colors, silhouettes and items two years in advance of the spring and winter seasons. About 150 people from the firm's global offices, spanning from China to Brazil to L.A., come together twice a year for what the group has dubbed "trends days."

At these events, forecasters from each region present their constituency's broader social and technological trends—for example, what's happening with the environment, and what new fabrics are available.

From there, WGSN begins honing in on "any new innovations that are really going to change the landscape of how we do business and the development of product," and whittle it down to three of four big ideas, said Jaclyn Jones, the firm's womenswear editor.

This season, for example, Jones predicts that the United States' strengthened relations with Cuba will inspire vibrant colors and palm patterns that reflect a sort of "Latin glamour."

"As time gets closer and closer we can be more specific," she said.

Trade shows, where the industry can take a look at new products coming out of the fabric mills, as well as precollections, which are typically shown a few months ahead of the spring or fall runways, also help the firm with its reconnaissance. And, Jones added, perennial favorites in fabrics or patterns will appear every spring or fall, but with a new twist.

"You can expect [florals] every spring," she said. "If it's not there, the customer will be confused."

'The wrong color is a markdown'

Some organizations are dedicated entirely to color. One such group is Carlstadt, New Jersey-based Pantone, whose eponymous Color Institute predicts color trends and consults with retailers and other companies about their use of color.

Since Pantone was founded in 1963, the group has created 2,310 shades—something Laurie Pressman, vice president of the Pantone Color Institute, refers to as a "universal color language."

"It is the single most important design element in creating a mood," Pressman said. "It's a silent language that you physiologically and psychologically respond to."

Similar to WGSN, Pantone works years in advance to identify societal shifts that influence how consumers view color. Take the color brown, for instance. Fifteen years ago, Pressman said, the hue conjured images of dirt and earth; but now, thanks to the "coffee culture" and fancy chocolates, "It's more about luxury."

Among the 210 new shades Pantone added to its collection in August—its first major addition in three years—were rocky road, fondue fudge and iced coffee.

Iced coffee is now projected to be one of the big colors for spring 2016, but the other top hues reflect a transition from the vivid bright colors that dominated the fashion scene recently. Pantone predicts more soothing colors will reign in 2016 like Rose Quartz, Peach Echo, and a blue called Serenity.

Retail trends: Denim is hot, 'bro tanks' are not

Once colors are added to Pantone's library, the group confirms that the dye is consistently repeatable, to ensure that two blue sweaters hanging side by side have the exact same hue. Retailers that have purchased Pantone's books can then either use the group's simple dye recipe in their manufacturing, or use Pantone's shade as inspiration for a dye they create themselves.

"It's not just about adding colors—it's about adding the right colors," Pressman said. "The wrong color is a markdown."

The 'secret formula'

As for identifying the key seasonal trends, Pantone compiles designers' sketches and groups the featured colors by family.

Once the looks hit the runway, demystifying the process of identifying trends is not that complex." said Vincent Quan, an associate professor at the Fashion Institute of Technology.

"Here's really the secret formula," he said. "You look at the upcoming calendar. Who are the fashion influencers? You pick a couple [like Diane von Furstenberg and Marc Jacobs]. … What you're looking for then is commonality."

From there, Quan said, the industry's job is making couture commercial. For luxury department stores buying designer duds off the runways, that means selecting the key pieces that can be tweaked to be more salable.

For fast-fashion shops, which can turn around similar looks in six weeks to three months, it means stripping a garment of the high-end materials and embellishments that would make it more costly—and time consuming—to produce.

At mid-tier retailers like Gap or Ann Taylor, it's about tweaking a silhouette to make it slightly more wearable, or turning a bold pattern into a single graphic for a T-shirt, Jones said. These influences, however, likely won't carry through for about a year.

For a mass merchandiser like Wal-Mart, Jones said it can take two or three years for the runways' influence to trickle down. And even then, it's at the most basic level, she said.

"To me, [how and when styles are adopted] depends on the store's customers and how privy they are to what's going on on the catwalks," Jones said.