The greatest thing you'll ever learn is just to love and be loved in return...
Baz Luhrmann had a goal in mind with Moulin Rouge, to make the viewer feel the same sense of being overwhelmed as a patron would have felt in the late 1890's, to connect the viewer to what was happening in a time long before ours through the use of modern music. In the first big number inside the Moulin Rouge, so much is thrown at the viewer all at once, bright colors, scenes not seen in daily life, tricks on the eyes, on the mind. Reportedly many viewers left theaters due to a sense of motion sickness.
In achieving this goal, Luhrmann, with costume designers Catherine Martin and Angus Strathie, strayed far from historical accuracy. Gone were the white undergarments of can-can dancers in a day when a bare ankle was something to get excited about, and in with the bright colors for skirts and different patterns for bloomers that resulted in modern viewers in an unchaste society to actually want to see up those skirts. At one point, 80 costumers were employed for the making and upkeep of the film's 300 costumes.
Interesting pieces of trivia: Courtney Love and Catherine Zeta-Jones were both considered for the role of Satine, and the late-Heath Ledger was considered for Christian; Ozzy Ozbourne was to provide the vocals to the originally-planned Green Fairy, "a long-haired muscle man with a giant sitar," but the Fairy's guttural scream at the end of her number was still provided by Ozzy; the necklace given to Satine by the Duke is the most expensive piece of jewelry ever created for a film - it contains a whopping $1,000,000 worth of diamonds.
Gowns with examples I made are marked by an asterisk (*).