Gentlemen Prefer Blondes was one of the movies I grew up with. Along with other Marilyn classics like Some Like It Hot and various Laurel and Hardy films, we watched it regularly on my stepfather's Betamax (which he hung onto despite its having long been rendered obsolete by VHS). So I knew all the words to "Diamonds Are A Girl's Best Friend" by the time I was about ten, and wanted to be a showgirl when I grew up.
The hot pink gown worn by Marilyn in the extravagant scene in which she sang "Diamonds" - surely one of the most iconic costumes in Hollywood history, which has continued to inspire copycat looks ever since - was just sold recently, surpassing all the estimates to go for a very healthy £213,000 ($312,000). Which to be honest doesn't surprise me - come on, it's Marilyn's dress! (Her "Happy Birthday Mr. President" shimmering sequinned gown sold for over $1.2million back in 1999).
While searching for images I also came across this page of Marilyn Monroe Costume Tests, which has shots of Marilyn in many of the costumes she wore in Gentlemen Prefer Blondes (oddly, not including the pink gown) and other movies - great fashion inspiration!
Vintage fashion - surely a girl's best friend!