As viewers of The CW's "The Flash" have noticed by now, Iris West is played by Candice Patton, who is African-American. While West is white in the comics (where she originated in 1956's "Showcase" #4) thankfully, no one seems to care very much. There was some very mildly negative fan reaction when Patton's casting was announced, but nothing like the backlash greeting the announcement that Michael B. Jordan would play Johnny Storm in Fox's 2015 "Fantastic Four" reboot, or the hullabaloo around Marvel's decision to launch new series starring a Black Captain America and a female Thor.
Maybe this is a sign that fans have become accustomed to (or even welcoming of) a more diverse superhero universe; the recent iteration of Ms. Marvel, who is of Pakistani Muslim descent, has been greeted with widespread goodwill, after all. Or maybe Iris is simply a sufficiently marginal or indistinct character that people aren't especially committed to any one version of her. She's undergone the usual round of improbable transformations and retcons over the decades, now reset to an acquaintance/love interest given DC's reported decree that no superheroes are allowed to get married (DC Co-Publisher Dan DiDio was quoted in 2013 as saying "heroes shouldn't have happy personal lives"). The television version of Iris is Barry's sort-of adopted sibling, though that hasn't prevented romantic relationship tension; and of course Barry's origin and costume, and to some extent his powers, have all been rejiggered.
Such alterations and resets are common in comics. When fans are upset about a Black Johnny Storm, they'll often invoke "tradition" as they naysay, but the truth is that there's no superhero tradition as hoary as changing your superheroes around. DC and Marvel's marquee characters have almost all been extant for four to seven decades, often in multiple media. The character I'm most familiar with, Wonder Woman, has been recast as a teen, as a toddler, lost her powers, gained them back, become a goddess, become her mother, had her origin revamped and re-revamped, become a UN representative, changed costumes -- and Lord knows what will happen to her in the movie version. And yes, there was even a Black Wonder Woman, briefly. For that matter, there's a long, uncomfortable tradition of turning minority characters white and making the superhero universe less diverse -- as seen in multiple instances including the recent casting of Vinnie Jones as Brick in "Arrow."
Based on that creative impulse to make everyone white, or on some of the reactions to female Thor or Black Captain America, you might think fans dislike or are embarrassed by this varied array of alternate Superwhos and reimagined Plasticwhats. In fact, though, comics creators and fans both seem to revel in them. Alternate earths and "What If?" stories proliferate, filed with future X-Men zapping back in time to wave at Victorian Batman or Russian Superman. The Green Lantern Corps seem to exist almost entirely as an excuse to have fun, alien versions of our hero -- Green Lantern as one-eyed plant, Green Lantern as bulldog pig guy, Green Lantern as planet. Grant Morrison has been a little more self-conscious about it in his runs with Batman and Superman, both weighed down with alternate versions of their heroes, but really, he's just picking up on a long-standing comics tradition of thematizing the narrative soap opera knots. Evil twins? Superhero comics laugh at your evil twins. We've got evil (and good, and future, and past) octuplets -- and that's just on this page.
Nor are these gleeful meta-duplications and variations confined to comics. "The Flash" winkingly includes 1990's TV Flash (John Wesley Shipp) as Barry's father, and there's every indication (including leaked set pics) that Professor Zoom, the Reverse Flash from the future, will make an appearance at some point. "Man of Steel" includes Kryptonian enemies, anti-Supermen and women to fight the Supergood. The most flagrant example in recent years, though, is probably "Iron Man 3," in which Tony Stark spends almost the entire time on screen out of his super-identity while everybody else -- buddy James Rhodes, girlfriend Pepper Potts, the President of the United States -- gets to take a turn in a suit of armor. The finale features countless remote-controlled empty suits of armor flying hither and thither, as Iron Man becomes everyone and no one, a mass-produced product that anyone can put on for a day. When Robert Downey Jr. quotes Ozzy Osbourne by declaring "I am Iron Man!" it doesn't sound triumphant or tortured so much as actively tongue-in-cheek, especially given the rumors that Downey may be nearing the end of his time with the character. Sure, he's Iron Man now, but someone else may be by the time we get to "Iron Man 4."
And since Iron Man has already been a black man and a woman, why shouldn't he (or she) be one again? It would be more consistent at this point to replace Downey with Lupita Nyong'o than with some other white dude. Superheroes are fantasy empowerment characters; that's not the only thing they are, but it's certainly part of the fun. You imagine what it would be like if you could put on that armor and fly away -- or as Candice Patton told CBR, "Put me in leather. Give me some kind of superpower. I would love it!"
Superhero narratives cater to that by saying, yes, you could be in leather and fly away, and also you, and you as well. Superheroes, as they're portrayed in superhero comics and films and narratives, aren't stable characters. They're potentials, and the enjoyment is in thinking about all the ways that potential can be fulfilled. A superhero who's faithful to the original isn't faithful to the original. If you want the true Iron Man, or the true Flash, or even the true Iris West, you have to let them be diverse.