Colman Domingo knows the healing power of art.

The day after his mother died in 2006, he auditioned for the rock musical “Passing Strange,” which dealt with the loss of a parent and marked his second Broadway outing.

“That show is the reason why I’m still living,” Domingo says now. “It sounds dramatic, but that’s the truth.”

It’s partly why the Oscar-nominated actor was so drawn to “Sing Sing” (in theaters Friday in 40 cities, expanding nationwide Aug. 23). In the heart-wrenching new drama, he portrays the real-life John “Divine G” Whitfield, who spent more than 24 years behind bars after he was wrongfully convicted of murder. While imprisoned at New York’s Sing Sing Correctional Facility in 1996, Whitfield co-founded Rehabilitation Through the Arts (RTA), a theater group helping incarcerated people gain critical life skills through writing and performing plays.

“I would love for audiences to walk away with a deeper understanding of the complex humanity you can find in a prison setting," Whitfield says. "With the resiliency of the human spirit, you will be amazed at the things we can do.”

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Colman Domingo was 'more vulnerable' than ever in 'Sing Sing' movie

Domingo, 54, has plenty of experience playing real-life people, from civil rights activists Bayard Rustin and Ralph Abernathy to Joe Jackson, Michael Jackson’s father, in an upcoming MJ biopic. But “Sing Sing” was unlike anything he’d done before: Not only was he portraying someone who is still alive, but he was also acting alongside a cast of formerly incarcerated men, many of whom passed through Downstate Correctional Facility, where the movie was shot.

“The great challenge was to fold myself in with these men. I didn’t want to stand out as an actor,” Domingo says. “They’ve had their (acting) training, yet they were bringing a raw sensibility of their own lived experience being in institutions like Sing Sing. It shaped my work in a unique way, and that’s why it’s hard for me to watch. It feels emotionally threadbare; I feel more vulnerable than I’ve ever been.”

The film traces Whitfield’s friendship with Clarence “Divine Eye” Maclin (playing himself), a reluctant recruit to the RTA program. It also depicts Whitfield's yearslong battle to prove his innocence: In a devastating scene set at a clemency hearing, he extolls the positive impact theater has had on his life. “Are you acting right now?” a parole officer asks incredulously, leaving him dumbfounded.

“That’s taken straight out of my parole board transcripts,” Whitfield recalls. “The way Colman hit that mark is just how I responded. I think he could win an Academy Award for that one scene alone.”

Domingo spoke with Whitfield a few times over Zoom before shooting started. The actor wasn’t interested in capturing specific mannerisms, but rather Whitfield’s essence: the way his eyes lit up when he spoke about his dance background, or recounted his days in the library poring through law books, “advocating for others as well as his own liberation.”

“I thought, ‘That’s an incredibly hopeful human being, who still believes the system can work – the same system that helped him be wrongly accused of a crime and landed him in prison,’” Domingo says. “When I observed that fullness of a human being, I was able to make decisions on how he moves through spaces and where his heart is."

Whitfield, meanwhile, calls the casting “a dream come true,” as a longtime fan of Domingo’s work in TV series such as “Fear the Walking Dead.” He remembers being “starstruck” and “babbling” during their first in-person meeting, where they bonded over their upbringings and tastes in food.

“I started realizing we had a lot in common,” Whitfield says with a chuckle. “I’ve always loved spinach, and he's the same way. As you know, most children don’t!”

The film inspired 'hope' for incarcerated men at Sing Sing prison

Shooting in a decommissioned prison, Domingo made a concerted effort to care for his mental health: taking frequent walks, buying himself flowers, and casting his longtime friend Sean San José in the film.

“I knew I needed a buddy to help ground me,” says Domingo, who is also an executive producer. “It does mess with you psychologically. These spaces are complicated – you see the way they’re built. There’s no breeze; the cells are so small; you can’t even imagine human beings living in that environment, no matter what someone had done. You lose your sense of space and time.”

Domingo’s warm and empathetic performance has won him rave reviews from critics, with many Oscar pundits predicting a second best actor nomination after last year’s “Rustin.” He also got plaudits from Whitfield, who thanked him for taking care of his story.

“It was almost like looking at myself in the mirror,” says Whitfield, who was eventually acquitted and released from prison. He has since published multiple novels and is shopping around a screenplay, which he describes as an “action-adventure love story.”

For him, the most meaningful part of this experience was screening the film for men at Sing Sing earlier this summer.

“You could see the hope in their eyes,” Whitfield says. “They look at us now and say, ‘You guys were right. There’s always hope at the end of the tunnel.’ ”