Lucy Liu as Joan Watson on Elementary. Photo: Best Possible Screen Grab/CBS

In the seventh and final season of Elementary, Joan Watson is blonde. The character’s style has constantly evolved alongside her detective career and partnership with Sherlock Holmes (Jonny Lee Miller), but in all her years on the show, there has been very little change to Lucy Liu’s locks. With just 13 episodes left, though, Joan has drastically altered her hair, which in turn means one last style shake-up for the best-dressed detective on TV.

Credit for that goes to costume designer Rebecca Hofherr, who has worked on the CBS procedural since its second episode in 2012, and who has guided Joan’s transformation from predominantly casual-leaning clothing to more structured menswear-inspired pieces. Hofherr spoke to Vulture about the narrative and fashion influences behind Joan’s costume evolution, including how they put their own stamp on an iconic duo and the sartorial challenges of shooting a 20-plus-episode season in New York City.

Photo: Giovanni Rufino/CBS

Joan’s styling was much more relaxed in the first year of Elementary. As his sober companion, her relationship with Sherlock was initially a professional commitment. She was not yet a detective and she was very much in the background of the investigation scenes. “Her clothing was very casual because that’s what the job called for,” Hofherr says. As Joan got more versed in the crime-solving world, her role shifted from sober companion to Sherlock’s protégée. By the second season, her costuming moved toward a slightly more sophisticated and buttoned-up approach. “As cheesy as it might sound, you need to put on a little more armor when dealing with the NYPD and all these criminals,” says Hofherr.

Photo: Jeff Neira/CBS

Joan’s wardrobe isn’t an either/or between suits and dresses, or even casual and business attire. She didn’t become a detective and suddenly stop wearing comfortable clothing. The suits reflect a change in Joan’s status and independence as an investigator, but dresses and sandals are still a vital style ingredient. During one Hofherr’s first conversations with Liu, they agreed Joan should “feel like a real New Yorker.” Expanding on this, Hofherr included staple items such as blazers or sandals, which most women have in their closets to dress an outfit up or down. “It was really nice to be able to incorporate them into a professional world for Joan,” she says.

Photo: CBS

Discovering the true cost of a TV character’s wardrobe is an eye-opening experience. Joan’s closet is definitely packed with high-end items — Hofherr’s go-to favored designers for Joan include Victoria Beckham, Saint Laurent, Isabel Marant, and Stella McCartney, with Rag & Bone as her signature bootee choice — but to ensure her clothing reflected that New Yorker aspect, Hofherr also shopped at Zara and H&M. “It was really important to do a mix,” she says. “I think that’s pretty much how everyone shops. I don’t think it’s realistic to only shop at high-end stores.”

Noticeable costume repeats tend to be outerwear, but Hofherr also uses staple investment pieces such as high-waisted black pencil Victoria Beckham pants. (Dressing them with an inexpensive top, she adds, is “a great way to get a lot of outfits out of a really expensive pair of pants.”) There is an aspirational element to Joan’s garments, but the high-low mixing reflects how a lot of people shop. Hofherr also notes with a laugh that “pretty much everything Lucy wore from Zara, I also own. I was like, Oh, I can afford that.”

Photo: Michael Parmelee/CBS

The one item that has appeared in all seven seasons? Joan’s red men’s Elder Statesman “house sweater.” Most people have a cozy garment that they only wear in the comfort of their own home, Hofherr explains, and Joan is no different. Sherlock and Joan’s brownstone home doubles as their office, but she wouldn’t be wearing suits at all hours of the day and night while solving a case. As Liu has worn this sweater so many times on the show, Hofherr says that not only has it molded to her body but it also has the pulls of a well-loved garment. It is also a color Joan doesn’t typically wear, which visually makes it a “nice change.”

Photo: CBS

Joan doesn’t eschew color, but a black-and-white motif runs through the first season to the last. Regardless of whether it is a suit, skirt, or a more casual outfit, sticking with the same color tone allows for experimentation with pattern. In the above outfit from season four’s “The Games Underfoot,” she wears a Saint Laurent polka-dotted tie with a checkered J.O.A. skirt and polka-dotted Ji Oh blouse. Sometimes the costume choice reflects Joan’s career, but on occasions like this one, it shows that Joan has a “fashionable side” too. “She can throw these things together and look really cute,” Hofherr says.

Photo: CBS

Two big style turning points emphasize Joan’s drive for equal footing with Sherlock as a detective. First came the ties, introduced at the end of season three. Suits followed, making their initial sartorial stamp in season five. The message is clear: Long gone are the days when Joan was Sherlock’s student. As with a lot of Joan’s costuming, she doesn’t stick to one specific suit-and-tie combo. In fact, the Marc Jacobs shirt above (which Hofherr got from one of her go-to sites, Shopbop) is a bit of an optical illusion, as it doesn’t even include a tie. Vests were thrown into the mix after Hofherr made the decision to stick with suits. It is also a nod to her relationship with Sherlock: Up to this point, Hofherr points out, vests have been Sherlock’s thing, so this costume mirroring is “a little nod to her respecting him so much.”

Photo: Michael Parmelee/CBS

“I went to all ends of the Earth!” Hofherr laughs when talking about the many ties Joan has worn on Elementary. Men’s offerings were out of the question for someone of Liu’s stature, as they are just too wide and long. She snapped up everything Saint Laurent and Gucci had on offer, but she also shopped at uniform companies, bought a few kids’ ties, and even made them in-house. Maybe a Joan Watson tie line should be next? “If all these designers are going to sell women’s suits, I would love for them to start making women’s ties,” Hofherr suggests.

Photo: Jeff Neira/CBS

Another later costume addition was the Victorian-style Isabel Marant blouse. In part, this outfit was a hat tip to the original Holmes and Watson, but it also added another variation on the suit theme. One of the biggest challenges when doing a show with a full 20-plus-episode order is obtaining enough clothing, particularly for a fashion-forward character like Joan. Hofherr says that she needs 50 outfits a month — on average, Joan has five changes per episode — and costuming was made trickier because designers don’t typically replenish their collections between seasons. “We end up making a lot of clothes based on designs we love and change a few things because I can’t find 20 Victorian-style blouses or 20 men’s-style blouses,” Hofherr laments. “I can find five, but then that’s it for four months.”

Photo: Jeff Neira/CBS

Fashion seasons are not the only Elementary costume challenge, as shooting outside in New York City from July to May means having to find clothing that fits all weather cycles. (The 13-episode final season was a bit easier, though, because they only shot until December.) Sherlock sticks to the same styles — “This guy would buy 20 of the same shirts, the same sport coat, and the same pants,” Hofherr says — and he has also worn the same Tom Ford winter peacoat for seven years. On the flip side, Joan has many changes, but she isn’t going to have a different coat for each outfit, as that is neither practical or realistic for either the character or the designer. Hofherr’s preference was to have between five and ten on hand: “If we got the coats fitted and ready to go we could just recycle them episode after episode.” Outerwear is something that is repeated across various seasons — including the Alice + Olivia coat above — but accessories like hats, gloves, and scarves are switched out to keep things fresh.

Photo: Jeff Neira/CBS

Sometimes the weather also dictates the type of hat required: “I originally got that hat because we were shooting outside one day in the rain and they didn’t want to have umbrellas,” Hofherr says. The wider brim of this Barneys-brand men’s hat has since been worn on a number of occasions, as has the tie-waist Marissa Webb windowpane check coat (which will reappear in the final season).

Photo: Jeff Neira/CBS

Of course, the story also dictates what Hofherr chooses for Joan. At the end of season six, creator Rob Doherty didn’t know if they were going to get renewed, so they shot two different endings. This particular Diane von Furstenberg dress fit both the ending we saw and the alternative they filmed — though Hofherr couldn’t provide any other details without spoiling the end of season seven as well. “I wanted it to be timeless, as I didn’t know if it was the last time we were ever going to see Joan Watson,” she says. “It was a little bit of an ode to all the Joans we have seen throughout the seasons. I felt a suit would have been a different look for that final scene.” No surprise, then, that it is also one of Hofherr’s costume highlights.

Photo: Jeff Neira/CBS

Hofherr couldn’t pick a single favorite outfit, but this one she considers to be the most significant. At the end of season three, Sherlock has almost killed a man and relapsed, but Joan’s loyalty doesn’t waver. “This is where we start to see the Joan that we will forever know,” says Hofherr. “And I think this is the best version of Joan too.” The pink skirt is by Roland Mouret and the shirt is Uniqlo, which is another high-low outfit mix. It also happens to be the first time Joan wears a tie, which is a huge style turning point.

Photo: CBS

Hofherr also spoke in depth about working with Liu, not only as an actress but in her role as a director. (She has stepped behind the camera six times on Elementary.) Referring to Liu as “one of the most inspirational women I’ve had in my life” — she also did the costume design on the Liu-starring Netflix rom-com Set It Up — she says Liu is “willing to take risks, but she knows exactly when to take them.”

Photo: Elizabeth Fisher/CBS

Which brings us back to the blonde mystery. Hofherr had already FaceTimed with Liu sporting her new hair color, but the styling was a task of its own. “She walked in for her first fitting of the final season and I didn’t recognize her,” said Hofherr laughing. They did plan fewer outfits than previous seasons’ fittings, she adds, “because we were figuring out what works with the blonde hair and what doesn’t.” Don’t worry: There are still plenty of outfits to come, particularly in the last two episodes. (Hofherr teased that Joan will have ten-plus changes.)

The signature black-and-white motif remains, including these fabulous Stella McCartney palazzo pants. “I always know it’s a really good outfit when all the crew members ask me what it is,” Hofherr says. That is the exact reaction Liu got when she stepped on set in this particular costume.