FORTUNE — If there’s any scenario in which it’s acceptable to wear a football jersey to the office, it’s probably when the home team is playing in the Super Bowl.
That’s the case this week for avid fans in Seattle and Denver, and many businesses are encouraging the fevered excitement. The football matchup is daunting defense (Seahawks) vs. dominant offense (Broncos), but on the business side it’s Emerald City tech vs. Rocky Mountain environmentalism. It’s rainy coastal corporations vs. thin-air, ski-bum bosses. It’s blue and silver vs. blue and orange.
On the Fortune 500 side, it’s powerhouse brands like Microsoft (MSFT) and Amazon (AMZN) vs. a slew of large but lesser-known companies like CH2M Hill and Newmont Mining (NEM). Englewood, just outside of Denver, is also home to the headquarters of Western Union (WU) and Dish Network (DISH).
Both states boast almost the same number of companies on the 2013 Fortune 500 list: Colorado has 10 to Washington’s eight. Consumers are more likely to know more of the Seattle companies: In addition to the aforementioned tech giants, the metro area is home to iconic Starbucks (SBUX), Costco (COST), and retailer Nordstrom (JWN). Also on the list: truck-maker Paccar (PCAR) and timberlands owner Weyerhaeuser (WY). Colorado has Arrow Electronics and metal packaging-maker Ball (BLL) among its 10.
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On the revenue side, the numbers aren’t as close: The eight Washington companies had total combined 2012 revenues of $289.5 billion, while Colorado’s 10 tallied $100.8 billion. As you’d expect, not all of those big Seattle moneymakers are eager to talk trash. Amazon and Starbucks declined. And a Nordstrom spokesperson wrote us, “We serve customers all over the country and do not want to disappoint those who may not call the Seahawks ‘their team.'” But some companies embrace the face-off.
CH2M Hill finds itself in a fun position: headquartered in Denver, but with a large office in Seattle. There, Seattle area manager Dave Sturtevant has struck a bet with the company’s CEO Jacqueline Hinman: If the Broncos win, Sturtevant will donate $2,000 of his own money to The Greenway Foundation, located in Denver. If the Seahawks win, CEO Hinman will have to contribute the same amount to Mountains to Sound Greenway Trust in Seattle.
In an email sent Tuesday to the Seattle office and obtained by Fortune, facilities manager Brian Rosell explained the bet (opening the letter: “Hey CH2M Hill 12th Man, are you ready for some FOOTBALL?”) and added another layer. In addition to the charitable contributions, new U.S. region director Patrick O’Keefe, based in Denver, will have to wear a Seahawks hat to an officewide brown-bag lunch in Seattle in February; if the Broncos win, Rosell will wear a Broncos hat to the equivalent event in Denver.
In addition to the bets, employees are all decked out today. “Attention Broncos fans, it’s time to ride!” read a loud, large-font email sent this week to employees on the Denver campus with Friday instructions. “We did it for the playoffs, let’s do it for the Super Bowl … Pull out that orange and wear it proudly!”
Western Union CEO Hikmet Ersek, a former professional athlete himself (he played basketball in Europe), is especially excited. “Manning’s leadership has transformed the playing field, setting a new tone for the Broncos,” Ersek tells Fortune. “Sunday’s game is the seventh time in franchise history that the Broncos have played in a Super Bowl. We’re bringing home the trophy, where it belongs.”
While Microsoft wouldn’t exactly send over trash-talk from CEO Steve Ballmer, the Seattle-based giant did clue us in on what it’s doing internally to get pumped up. This week’s Seahawks spirit-setting around its central employee campus, The Commons, included 12th Man cookies, giving out 100 Seahawks “swag packs” from the company store, and dispersing Seahawks scarves from Bing. All receptionists, shuttle drivers, and cafe workers are decked out in Hawks gear today, and last week the winner of a “Big Game Blitz” employee contest won two tickets to the Super Bowl.
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The startups in these cities aren’t keeping quiet either. At Seattle-based Porch, which aims to use big data to improve the home-improvement industry, yesterday was “Blue Thursday.” (Every Friday is “Blue Friday” for Seahawks nation during the season, but Porch employees wore the Hawks colors all week.) Porch founder and CEO Matt Ehrlichman will be attending the Super Bowl and wrote a blog post on the company website this week in which he enumerates leadership tips embodied by Seattle coach Pete Carroll. He writes that in building Porch, he “borrowed many of the philosophies that Pete Carroll preaches.”
Football fever is just as high at Denver startups — even if some try to be classy about their fandom. Steve Swoboda, co-founder of video advertising startup SpotXchange, remembers last year, when the company rented a suite at MetLife Stadium in New York for the Broncos vs. Giants game. “It turned into a blowout. Most of the SpotXchange crew at the game were Broncos fans, but our guests were largely Giants fans, so we had to tone down our enthusiasm,” he tells Fortune. “Colorado is a pretty friendly state … but make no mistake, we’re fierce on the battlefield and this is one week SpotXchange won’t be shy about showing our Broncos pride.”
Both teams, clearly, will have rowdy supporters from corporate America cheering for them on Sunday. Of course, if you apply the corporate angle to the game’s two quarterbacks, that one isn’t much of a contest: Peyton Manning, hard to avoid on your television even during the football offseason, is loaded up with far more brand endorsement deals than his counterpart Russell Wilson. (See: The 10 highest-earning U.S. athletes.) But on the field, all of that will just be background noise.
