“The sun always shines on Beverly Hills, but not on everyone,” Camille Grammer says in the opening line of “The Real Housewives of Beverly Hills,” which premiered on Bravo in 2010. For the majority of its first nine seasons, the reality show shined its light on a certain type of woman: rich, opinionated and white.

Outside of one Latina cast member — Joyce Giraud, who appeared on one season of the show, in 2013 — the franchise has featured a racially homogeneous cast throughout its run.

But “The Real Housewives of Beverly Hills” is about to look a little different. Bravo announced in August that Garcelle Beauvais, an actress and former model, will join the cast next season. She will be the first black woman to be featured on the show.

“As the first African-American Housewife in the Beverly Hills franchise, I am honored and humbled by this awesome opportunity to exemplify the fact that Black Girl Magic lives and thrives in every ZIP code,” Ms. Beauvais said in a statement on Bravo’s website.

One ZIP code down, many more to go. The “Beverly Hills” franchise is not an outlier in the “Real Housewives” series, whose casts are often divided on racial lines.

Six Degrees of Separation

Each iteration of “The Real Housewives” follows women in the geographical location for which it’s named as they navigate relationships with each other, their families and often themselves.

The premise is that the “housewives” (a term that is interpreted loosely on the series — many of the women have jobs outside the home and aren’t married) are friends, but in reality, some of these relationships begin when the women are cast for the shows.

Many of the “Real Housewives” iterations have remained segregated. On “Atlanta” and “Potomac,” you’ll primarily see black women, but women of color have largely been absent from “Orange County,” “New Jersey,” “New York City” and, until recently, “Beverly Hills,” and “Dallas.”

The current season of “Dallas” features a newcomer, Kary Brittingham, who is originally from Guadalajara, Mexico, in its cast alongside five white women, including LeeAnne Locken.

In a midseason trailer released last week, Ms. Locken can be seen saying, “But the little chirpy Mexican has to have her way,” referring to an altercation with Ms. Brittingham, and later, “C’mon, Mexican. I thought you were all Mexican and strong!”

The comments don’t go unnoticed. The cast discusses her derogatory language throughout scenes in the trailer.

When a producer asks another housewife, Brandi Redmond, “Do you think she’s a racist?,” referring to Ms. Locken, Ms. Redmond sighs before the video cuts to black. Bravo did not respond to a request for comment, and Ms. Locken has denied the characterization on Twitter.

Not so subtle references to race have cropped up time and again on the “Housewives” franchises. During the 10th season of “New York City,” Luann de Lesseps, a cast member, proudly sauntered into a costume party, looking at other attendees with sultry, bedroom eyes. Her head was held high and covered with a two-foot-tall Afro wig. Her skin was quite noticeably several shades darker than it usually was.

When she approached her friends, however, she became visibly annoyed — offended, even — that no one was able to correctly guess that she was dressed as Diana Ross. Unfortunately, this was the closest that “New York City” has ever come, in its 11-year history, to featuring an African-American woman on its cast.

Because of the hyperbolic hairstyle and self-tanner that had developed deeper than her own voice, Ms. de Lesseps was accused by fans on Twitter of being in blackface. She later appeared on “Watch What Happens Live,” Bravo’s late-night show, and denied that she had done anything wrong. Still, she apologized, saying, “I love Diana Ross. I totally respect Diana Ross. It was really kind of a tribute to her. It was Halloween!” She added that she applied no additional color to her skin, other than bronzer, and “would never dream of doing a blackface, ever.”

Only one “New York City” cast member, Carole Radziwill, acknowledged the transgression on the show before it was mostly forgotten about for the rest of the season.

But what if there had been an African-American woman on the cast? And, of course, the bigger question: Why has there never been a black woman on the cast of “New York City”? According to the most recent United States census, 24.3 percent of New York City’s population is black, 29.1 percent is Hispanic, and 42.8 percent is white. If less than half of the city is white, why is 100 percent of the cast of “The Real Housewives of New York City” white?

And are the people making the show concerned about this?

“Absolutely, it bothered me,” said Heather Thomson, who was a cast member from 2012 to 2015. “I advocated for more diversity while I was on ‘The Real Housewives of New York City,’ not only to showcase the reality of NYC, but also my own true circle of friends.”

Her professional and social circles were notably more diverse than some of her castmates. Before founding her shapewear company, Yummie, she was the founding design director of Sean Combs’s label Sean John and worked closely with Jennifer Lopez and Beyoncé to develop and introduce their clothing lines. If ever there were a white bridge to an elite crowd of affluent nonwhite women in Manhattan, Ms. Thomson was it.

Ms. Thomson said that after her first season on the show, she recommended several women of color to producers. The producers “were wide open to it,” she said, and they contacted the women she recommended, but ultimately “were not successful in finding the right individual to fill the void.”

It’s unclear why producers were unsuccessful in casting a woman of color for “New York City” in those years or in the years since. When asked about its casting process, a spokesman for Bravo said that its “docuseries follow groups of friends who are organically connected, often through long, pre-existing relationships but in some cases only casually through a wider social circle or six degrees of separation.”

Although producers seek casting recommendations from current cast members, they don’t do so exclusively. Ms. Thomson herself was contacted by a casting agent and she had not known any of the cast members before filming.

Similarly, Ms. Giraud and Carlton Gebbia, another former “Beverly Hills” Housewife, met their castmates for the first time on camera. Heather Dubrow and Shannon Beador, of “Orange County,” were both introduced to their castmates on camera.

Ms. Radziwill, who starred on “New York City” from Season 5 to Season 10, also did not know her castmates before filming. She was cast on the show by the Bravo executive and television host Andy Cohen, of whom she was an acquaintance. (Bravo declined to make Mr. Cohen, an executive producer of the “Real Housewives” franchise, available for a comment for this article.)

Michael Arceneaux, an author, culture critic and Bravo fan, said some of the “Real Housewives” casts accurately reflect the demographic of affluent women in their respective regions. “Maryland has the highest concentration of black wealth,” Mr. Arceneaux said, which is reflected in the racial makeup of “Potomac.” “Atlanta,” which has featured a white cast member, Kim Zolciak-Biermann, is also in line with the demographics of its namesake city.

Ms. Zolciak-Biermann was part of the original cast when “Atlanta” started in 2008 and stayed on the show until she left for her own spinoff in 2012. (“D.C.,” which featured a black cast member among a group of white women, was canceled after one season. “Miami,” which featured white and Latinx women, was canceled after three seasons.)

“Atlanta” has had its own issues. In 2009, Nene Leakes orchestrated a professional photo shoot for her fellow castmates. The concept was supposed to be “alter-egos” in which the women were to model the two sides of their personalities, and Ms. Leakes requested that Ms. Zolciak-Biermann pose in blackface for one of hers. Unlike Ms. de Lesseps, Ms. Zolciak-Biermann did not dress up as a black woman on national television.

That doesn’t mean there haven’t been racial tensions between Ms. Zolciak-Biermann and her castmates over the years. After returning to the series in 2018, Ms. Zolciak-Biermann was accused by some of her castmates of making racist remarks during that season’s reunion episode. She denied the accusation in an expletive-laden tirade to Mr. Cohen backstage.

In another cringe-worthy episode, it was revealed during a historical tour of Savannah, Ga., that Porsha Williams, a granddaughter of the civil rights activist Hosea Williams, believed that the Underground Railroad had been a literal train, on railroad tracks.

Beyond ‘Housewives’

Overall, Bravo’s shows offer a lot of diversity, arguably more than most other television networks. There are shows featuring black people, white people, Muslim, Asian, Latinx and L.G.B.T.Q. people.

Many of its series highlight specific ethnic pockets within our society. For example, “Shahs of Sunset” focuses on a group of Persian-American friends in Los Angeles who share a culture and a set of traditions that bond them.

Similarly, “Texicanas” follows a group of Mexican-American women in San Antonio, which has one of the largest Latinx populations in the United States. “Family Karma,” announced earlier this year by Bravo, will document the lives of “several multigenerational families originally from India who are now living in Miami.”

Then there’s “Southern Charm,” which documents a group of modern-day Southern gentility in Charleston, S.C., all of whom are white, most of whom are the recipients of generational wealth and some of whom still own their families’ plantations, where they host parties, fox hunts and oyster roasts.

And while there are some shows in the Bravo lineup that feature diverse casts — competition shows like “Top Chef” or “Project Runway” — the issue of segregation is considerably noticeable among the network’s crown jewel, “Real Housewives,” and its spinoffs.

One such spinoff is “Vanderpump Rules,” which is set in a restaurant owned by Lisa Vanderpump, formerly of “Beverly Hills.” In 2015, there was an attempt at diversifying the cast with the hiring of Faith Stowers, a black woman. According to Ms. Stowers, this can be traced directly to Ms. Vanderpump, an executive producer of the show, who hired her to work at the restaurant in 2015.

“When I first got there, Lisa did have a sit-down with me and her publicist,” Ms. Stowers said. “They just told me straight-up, ‘We don’t have a lot of color on this show, and you would make a good asset to that.’”

In Ms. Stowers’s view, her casting was less about diversifying the show and more about Ms. Vanderpump’s public image as an equal opportunity employer. “I kind of knew going into it that I would be filling in for the spot of, like, showing that she hired people of color.”

But things didn’t work out all that well for Ms. Stowers, who appeared on just one season of the show. Of her experience, Ms. Stowers said, “I definitely felt like I was being treated differently from everybody else.”

Evolution Media, the production company that produces “Vanderpump Rules,” “Beverly Hills” and “Orange County,” did not return a request for comment.

It’s unclear if any of the production companies involved in the “Real Housewives” franchise have any intentions to diversify other casts. For now, we’ll have to watch what happens.