This is not simply a case of color-blind casting where the audience is supposed to ignore the discrepancy between the race of the character and the performer portraying him or her. With African-American actor Underwood playing Stanley, the character's last name of "Kowalski" has been dropped, as have references to his being Polish.
Parker's Blanche DuBois is also African-American, but with her sister Stella played by Latina actress Daphne Rubin-Vega, there's a suggestion of mixed-raced ancestry for the DuBois family. This could even account for Blanche's prejudicial views against Stanley that are class-based in the script, but have racial overtones here -- particularly when she refers to him as "apelike."
But at the end of the day, it's the actors' ability to bring Williams' wonderful play to life that makes the production so effective. Parker impresses from her first entrance, displaying a mix of fragility, bewilderment, and sense of entitlement as Blanche arrives at her sister's home in New Orleans. The actress charts the hairpin turns in Blanche's interactions with Stella, Stanley, and her newfound love interest, Mitch (Wood Harris), and her rendition of the character's ultimate tragic fate is quietly affecting.
Underwood exudes confidence and sexiness as Stanley, who is portrayed as a flawed but still likable fellow. He has great chemistry with Rubin-Vega's Stella and the antagonistic relationship between Stanley and Blanche is believable, even if the staging of their fateful confrontation towards the end of the second act (fight choreography is by Rick Sordelet) is not as tension-filled as it should be.
There's some nice work from the supporting ensemble, as well -- particularly Aaron Clifton Moten who is delightful in the fairly minor role of the Young Collector with whom Blanche flirts when he stops by with his newspapers.
Adding to the power of this production is the original music from Grammy winner Terence Blanchard. The jazzy score nicely complements the action, and is well integrated with Mark Bennett's sound design.
Paul Tazewell's costumes are similarly effective, particularly the striking ensembles worn by Blanche. Eugene Lee's set establishes the cramped and not-so-well-off living conditions for Stanley, Stella, and Blanche without making it look too squalid. Edward Pierce's lighting is terrific, establishing the hours of the day and night for each scene, as well as contributing to the show's overall mood.