While Joan Harris has been slaying the sartorial competition on the first three episodes of season 4's "Mad Men," Peggy Olson was the style star last night.

The brainy copywriter opened the show in an extremely covetable piece that could easily be worn today: a bright blue three-quarter-sleeve blouse with neat pleats down the front and a darling Peter Pan collar.

She paired it with a more sophisticated hairstyle, red lips, and a skirt in one of her signature (yet slightly cringe-worthy) hues -- mustard.

The same unfortunate color pops up again on Peggy throughout the episode -- first on another Peter Pan-collared blouse with a bowed neck that she pairs with a black jumper, and again on a striped sweater she wears to a beatnik party, where she also shows a bit of skin by ditching her nylons for a pair of knee-baring high socks.

We let the mustard incidents pass, however, after she ends the show in a buttonless short-sleeve Smurf-blue dress with a sharp, bright white collar. Note to Peggy: Blue is most definitely your hue.

While Joan's presence wasn't played up so much this episode, the red-haired siren made an appearance in one of her waist-cinching blue dresses seen in previous episodes. (Watch "Mad Men" costume designer Janie Bryant explain why using past costumes helps character development.)

Surprisingly more interesting than Joan were the other secretaries, who got a lot of face time and showed off their tiny figures in body-hugging frocks in pretty lavender, blood orange, emerald green, turquoise, and some uglier paisleys, browns, and '60s-tastic plaids.

Want to channel a signature "Mad Men" beauty statement also worn by Julianne Moore in Tom Ford's "A Single Man"? Check out at Karen Robinovitz's step-by-step guide to the sexy cat eye.