Dreary concrete walls enclose a small outdoor space where several paint-splattered teenagers gather, ready to start a day’s work. The students — members of the nonprofit Publicolor program, which pays them to paint — are shy and quiet as they begin splashing a bright yellow on the walls with steady, experienced hands. Eventually, hip-hop music begins to drift from the indoor workstation where the flashy buckets of paint sit, and the teenagers relax as they transform the vacant urban space into a playground for formerly homeless children in Brooklyn.

“This color ain’t really that bright depending on how the light hits it,” a recent high school graduate, Angel Pino, squinting critically at his marigold-yellow part of the wall, said. Mr. Pino is confident he knows what he’s talking about because has been with the program for six years and is designated a “master painter,” which means he can take contract work and is paid a higher wage.

Not that Mr. Pino would necessarily want to take professional painting jobs. He said he did so once with his stepfather, and didn’t like it.

“Here we’re helping the community, there you just knock out the job and go home,” he said. “Here we interact more.”

Going on its 13th year, Publicolor is older than many of its participants, and has recently expanded into Pittsburgh on the strength of its success in New York City. Publicolor is funded in part by the Department of Education, and has been one of Mayor Bloomberg’s favorite causes. Some of its popularity is due to the reputation of its founder, the industrial designer Ruth Lande Shuman. In a telephone interview during which she spoke of Publicolor’s students as her “youngsters,” Ms. Shuman described an organization that is cautiously expanding, wary of sacrificing the quality that is the hallmark of its success.

“Theoretically, I would love to accept more,” Ms. Shuman said. “Practically, I need to make sure that that kind of growth isn’t going to dilute the program and isn’t going to dilute the very important sense of community that we’ve built.”

Selectivity is a cornerstone of the institution. Publicolor recruits students as they paint struggling schools in neglected neighborhoods, transforming prisonlike concrete walls with tropical, Popsicle colors approved by Ms. Shuman. The students who show the most promise are asked to join Publicolor once their school is painted, and they enter the program as paid rookies. More than 80% of Publicolor’s participants go to college — Mr. Pino will attend Fordham University while also serving in the National Guard. Most are the first in their families to attend college.

This summer, students take classes at the Pratt Institute during the mornings and paint community spaces in the afternoons.

“It’s not really school, it’s art,” the 17-year-old Omar Liriano said of the graphic design courses.

The summer is a bit of a break from the rigors of the program, which also provides SAT tutoring and placement in internships. Keshawn Whiteman, 13, said that the painters don’t get graded on their work over the summer as they do during the school year, which makes the painting more relaxed.

Meanwhile, the staff at the day care center peeked out their windows to watch the teenagers convert their space — vacant since it opened in 1991 — into a play area.

“At first we were a little worried about the notion of all these high school kids with all this paint,” the executive director of Brooklyn Community Housing and Services, Jeff Nemetsky, said. The employees were soon won over.

“It’s wonderful,” a day care employee, Helen Rada, said. “We’ve been waiting for a while.”