I'm sorry, but there is no solid "representation" argument to make. Either you care about being true to source material, or you don't. If a character isn't black, or Asian, or Latino, or any other "non-white" thing, then they shouldn't be cast as such. Period. It isn't "a new take on an old favorite", it's lazy, pandering casting practices.

If they want more "representation", then make new properties or characters who are those things. Aquaman is a white-looking blonde, blue eyed man. That's how he should be cast. Iris (and Wally) West, are pale white, red haired people. Not black. So they should be cast as what they are. The most egregious and lazy as fuck examples, are "Domino" and "Starfire". At least they KINDA tried with the outfit of Starfire, but the thing is, it was more important to them to show that "SEE WE HAVE A BLACK WOMAN", than it was to be true to what the character actually is: IE NOT a black human. Starfire is a goddamn alien, with goldish/bronze skin, red hair, and glowing green eyes. NOT a black chick in a hooker outfit, with a shitty pink dye job.

Domino honestly blew me away, because they actually bothered and put in EFFORT for Deadpool to look like Deadpool, and Cable to (mostly) look like Cable. But Domino? It's like they didn't even look at the comic. She's just some black chick, with a black accent, and an afro, and a weird little white loop around one eye. Yes, she vaguely has "luck powers", but her look is the height of Hollywood laziness. In BOTH cases, they could have cast a black actress if they really wanted to, but for god's sake, put them in MAKEUP, and at least TRY to make Starfire look like a bronze alien, and Domino look like a stark white woman with a black eye patch, and ZERO afro. It is pathetic when cosplayers with limited funds can do a spot on job, but Hollywood with millions and professional makeup artists and costumers, can't or won't.

And for the record, I'm a stickler even for crappy casting among "white" actors. It was lazy as hell to cast a brown eyed, brown haired woman as Jean Grey. It was lazy as hell to cast a blonde as Mary Jane Watson and then dye her hair. And then ironically cast a redhead, who by the way would have made a better Mary Jane in the first place, as a (bleached) blonde Gwen Stacy. It even boils down to lazy little shit, where it's obvious they're not even paying attention or just don't care, where they have, say, a brown eyed boy, playing the child version of blue-eyed Robin Williams' character. They do that a LOT in movies, with child and adult versions of characters with different eye colors, as if they just expect the audience to be too stupid to notice. Does it matter all that much? No, not really. But it's STILL incredibly lazy attention to detail, and lack of care in your own work.

But to reiterate my earlier point, as someone of "color" (though I hate that term) myself, if they want more "representation" of non-white/etc. characters in things, then MAKE them. It is lazy and insulting to remake a pre-established character, and shape them into what YOU want them to be, just to meet some kind of imagined quota. I'd be mad as hell if they cast Blade or Falcon or Cyborg as white, or asian, or arab. And I'd be just as pissed if they cast Superman or James Bond or Harry Potter, as a black actor.

People care too much either way.

Doesn’t really matter. Each new iteration is a new interpretation or new view of the story. They should find whoever best fits their vision for that telling, not what was originally told. I don’t want to see the same thing over and over again, a little change here and there is a good thing!

If the race is stated in the source material then that should be the race in the show. Trying to change the race to be "diverse" is dumb. Like if the character is white in the source material then they should be white in the show. If they're black in the source material, then they should be black in the show. Not hard to do. That's just my 2 cents though.

If that's the case then any race is fair game. 

It really depends on how important race is to the character in question. If being white is a key focal point of the character, then I would hope it's left the same, assuming they're planning to do a faithful adaptation. If it's just white noise (heheh), then I couldn't care less. I always thought it thought it was annoying how much attention the race swapping in the Netflix Death Note received, when I was far more concerned with the characters acting completely foreign to their manga counterparts. Turning a quirky sleuth known for his anonymity into someone who gives public speeches annoys me far more than changing something as arbitrary as his skin tone.

Of course, people making adaptations have no obligation to follow the source material 1:1 either...personally I just wish to see the spirit of the original story and characters intact. If that doesn't happen, then said adaptation simply doesn't deserve my attention.

Bolder = Like when Dave Jaffe (creator of God Of War) said he’d love to see Djimon Hounsou play Kratos in a live film and everyone lost their sh!t. I mean, he created it so he can do what he wants. 

You’re the first person I’ve seen make noise about the Aquaman switch. For months people griped about Starfire and I’d “what about?” Aquaman and people would say it’s OK because he looks cool. 

I guess I'll never understand how a person's skin tone can change the quality of a movie.

sometimes a change of colour is done for comedy.... very poorly.

I know this isn't a case directly related to what the OP is referring to, but while movies like this are seen as fine but the reverse of it would be deemed horrifically racist then the issue of skin colour in Hollywood is not on equal footing to begin with.