Colorado Rockies fans cheer on their team during Game Three of the National League Division Series playoffs against the Philadelphia Phillies earlier this month at Coors Field in Denver. Tonight, the Rockies’ stadium hosts its first World Series game.

AP / Bill Ross

When Dustin Pedroia crushed his leadoff home run over the Green Monster on Tuesday night, the crowd at Denver’s Pour House Pub went wild — and not just because it meant a Red Sox lead.

Suddenly, owner Storm Ireland and his staff were running around the room filling shot glasses. This is a Red Sox bar, an oasis for Sox fans in a sea of purple-clad “Rocktober” madness in Denver. And at the Pour House, every Sox home run means a free shot of Tullamore Dew Irish Whiskey for the entire bar.

“My bar’s been crazy, because we’re a Red Sox bar, and all the Sox fans come out here,” said Ireland, who founded the bar with his younger brother five years ago. “We’ve got 300 people in here both nights going crazy.”

The Colorado Rockies’ shocking September and October run has catapulted the 14-year-old team to the top of the local sports scene, and the streets are constantly crammed with fans in purple Rockies gear.

But with the World Series shifting to Denver tonight and the Red Sox up two games to none, it’s expected that pockets of red will start to crop up inside the mass of purple as Red Sox Nation heads west to make its mark on Denver.

Ireland, who hails from the Boston neighborhood of Jamaica Plain, modeled his bar on Boston’s Pour House to give transplanted New Englanders a place that feels like home in a city loaded with classy lounges but lacking neighborhood pubs tailored to “watching the game.”

Outside of the few small Sox-friendly places, like the Pour House and the Blake Street Pub, New Englanders visiting Denver to cheer on their Red Sox will find they’re in for some culture shock.

To start with, there’s the altitude, which will require an adjustment period from players and fans alike, said Robert Mazzeo, an integrative physiology professor at the University of Colorado at Boulder.

“At altitude you have lower barometric pressure and, as a result there’s less oxygen per liter of air, so oxygen can become a limiting factor during high-intensity exercise,” he said. “If someone’s going for a triple, by the time they get to third they’ll be sucking air,” he said.

After a day or two of acclimatization, the Red Sox players should be fine, Mazzeo said. But the altitude may be a bigger hazard for some Sox fans: the mile-high elevation also heightens the effects of alcohol, Mazzeo said — so watch out for those free shots of Tullamore Dew.

“We say a golf ball goes 10 percent further at altitude — and so does a cocktail,” said Rich Grant, spokesman for the Denver Metro Convention and Visitors Bureau.

While Denver prides itself on having more than 100 local beer brands, it’s the dining options that may surprise New Englanders. The Rockie Dog might not measure up to the Fenway Frank, but the home of the Rockies, Coors Field, offers some choices that may shock Rhode Islanders who think the quahog and the stuffie are as exotic as it gets. Watch out, in particular, for the “Rocky Mountain Oyster,” a Western delicacy that makes use of bull testicles — they are usually peeled, coated in flour, pepper and salt, and then deep fried.

Perhaps most perplexing of all to the Rhode Island visitor, however, is that in Colorado there’s none of the travel phobia that defines the Ocean State.

“Things are bigger here. We don’t think anything of driving to Vail for the afternoon, and it’s 100 miles,” Grant said.

At the same time, Red Sox fans may have to shelve some misconceptions about the city of Denver. For starters, the fallacy that it’s cold in Colorado.

What few East Coasters realize, Grant said, is that Denver’s average October temperature is actually 4 degrees warmer than Boston’s.

The Denver area is very dry and receives little precipitation or cloud cover, and the sun is out most of the time. The sun’s constant glow warms what could otherwise be a cool climate.

“The temperature might be 60 degrees, but when you’re in the sun, it’s 80 degrees,” he said. “It was 80 degrees yesterday, it really was,” Grant said, though he acknowledged that a cold snap is expected this weekend, when temperatures should drop into the 40s.

Meanwhile, the Rockies’ recent success has helped them raise the profile of the entire city, and vault past the Denver Broncos to become the city’s sports darling.

The World Series is a coming-out party of sorts for Denver. Next summer, the city is hosting the Democratic National Convention, and 1,200 more hotel rooms are under construction. This week, a Ritz-Carlton hotel opened. The city is building the nation’s biggest light-rail network. And with Monday Night Football scheduled to feature the Broncos at Invesco Field the same night as a potential World Series Game 5, the 8,000 hotel rooms downtown are packed full of fans and media, Grant said.

“It’s pretty insane. We’ve never really experienced anything like this,” he said.

Tim Smith, a former Providence resident who has lived in Denver for the past two years, said that Rockies fervor has certainly taken over the city, but that it’s a different vibe than what he remembers from cheering the Red Sox to their 2004 World Series victory.

The Rockies, founded in 1993, have the same underdog mentality as the Sox did, but they don’t have the same history hanging over their heads, giving the fan base a more hopeful, familial mood.

“There’s a really good buzz around here, they’re really behind their team,” Smith said. “Everyone in the street is like, hey man, go Rockies. It’s got kind of that feel to it, where it’s more homey — everybody back East is die-hard, through and through, punch-you-in-the-mouth-if-you-say-otherwise Sox fans.”

In Denver, Smith warned, people are almost disconcertingly polite, even to the supposed enemy — which he found jarring at first.

“I actually made the mistake of wearing my Red Sox hat, and people were giving me hell,” Smith said — but it was only gentle ribbing, not the kind of treatment a Red Sox fan might face in New York, for instance.

“They’re not hostile here,” Smith said. “They don’t have enough to be hostile about yet.”

As for who he’s rooting for?

“It’s a great question. I’ve always been kind of an underdog guy anyway — which is part of why I was rooting for the Sox in 2004,” he said. “My heart is with the Red Sox, but this is a young team making their first step into baseball history, and I kind of want to be a part of that.”

dbarbari@projo.com