A brochure for the University of Michigan features a vision of multicultural harmony, with a group of students from different racial backgrounds sitting on a verdant lawn, smiling and conversing.

The scene at the undergraduate library one night last week was quite different, as hundreds of students and faculty members gathered for a 12-hour “speak out” to address racial tensions brought to the fore by a party that had been planned for November and then canceled amid protests. The fraternity hosting the party, whose members are mostly Asian and White, had invited “rappers, twerkers, gangsters” and others “back to da hood again.”

Beyond the immediate provocation of the party, a sharp decline in Black undergraduate enrollment — to 4.6 percent of the student body in 2013 from 6.2 percent in 2009 — and a general feeling of isolation among Black students on campus have prompted a new wave of student activism, including a social media campaign called “Being Black at the University of Michigan” (or, on Twitter, #BBUM). Members of the university’s Black Student Union have petitioned campus administrators to, among other things, increase enrollment of Black students to 10 percent.

Similar episodes and tensions have unsettled colleges including Arizona State; the University of California, Los Angeles; the University of Mississippi; and Dartmouth.

In the news media and in popular culture, the notion persists that millennials — born after the overt racial debates and divisions that shaped their parents’ lives — are growing up in a colorblind society in which interracial friendships and marriages are commonplace and racism is largely a relic.

But interviews with dozens of students, professors and administrators at the University of Michigan and elsewhere indicate that the reality is far more complicated, and that racial tensions are playing out in new ways among young adults. Some experts say the concept of being “postracial” can mean replicating some of the divisions and insensitivity of the past, perhaps more from ignorance than from animus. Others find offensive the idea of a society that strips away deeply personal beliefs surrounding self-identification.

“There’s this preconceived notion that our generation is postracial, but there’s these incidents that happen constantly that disprove that point,” said Zach Fields, a business major here, who is White. He attributed many high-profile incidents — including a number of fraternity parties nationwide that have used racist symbols, including watermelons and gang signs — to ignorance. “I feel like they don’t mean to be so offensive,” Mr. Fields, 20, said of the party organizers. “It’s not a conscious racism. It’s subconscious.” Tyrell Collier, 21, the speaker of the Black Student Union, who is majoring in sociology and Afro-American and African studies, said racial tensions on campus had been mounting for months.

“There was a very tense climate brewing all semester, and I think the party was just the peak,” he said. Mr. Collier added that his group, which spearheaded the popular social media campaign, had received inquiries from other Black student groups around the country looking to use similar tactics. “We’re clearly not postracial,” said Tiya A. Miles, chairwoman of the department of Afro-American and African studies. “Sometimes I wonder if having a Black president lets people feel like that gives them cover. It absolves people of being prejudiced.”

The number of complaints related to race and ethnicity filed against colleges and universities rose to 860 in 2013 from 555 in 2009, according to the Office for Civil Rights at the federal Education Department. Some experts believe that the increase reflects, at least in part, the role of social media in creating and then publicizing episodes.

Read it at NY Times.