EXCLUSIVE

Say this for famed virgin Colton Underwood, America's next 'Bachelor' knows his way around first base ... just look at his mile-high make out!

We've obtained footage of Colton and one of his suitors on a super cute one-on-one date Monday at the Denver Milk Market ... which is really interesting because they're in Colton's hometown.

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Check out the clip ... Colton and his date have great chemistry ... holding hands, flirting and kissing as they shop for pasta, salmon and wine. They were also spotted playing corn hole. Take notes, fellas. Pretty solid date.

It's the first time we've seen Colton in public since the start of filming ... and it looks like he's taking a page from Rachel Lindsay's book.

The mystery girl is one of the lucky ones ... she's clearly made it deep into the season.