Dana Weiss of Possessionista.com is InStyle.com’s correspondent on all things Pretty Little Liars  fashion for Season 4. Scroll down to read this week’s exclusive update on what the ladies of Rosewood wore.

This week’s black-and-white episode of Pretty Little Liars could have been problematic for costume designer Mandi Line, who has a penchant for contemporary fashion, but she insisted that it was possible to recreate ‘40s fashion, while still staying true to her characters’ personal style.

“I did a lot of research to make sure I could find something like a striped dress in 1940s style, or a sexy dress with polka dots and big shoulders. I needed to be able to say that I could still make the characters look like themselves.” And as for the black-and-white factor, the color-obsessed stylist had a solution for that too. “We tested every outfit using the black-and-white filter on Instagram.” Click through for more Pretty Little Liars outfit exclusives.

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—Dana Weiss of Possessionista.com