Or an editor might say, I don't care if it's racist, we are speaking to a particular audience, as kb points out above.

I really don't see the issue with this if it is indeed the case. Free speech is free speech. If you want to push out racist content (because it sells), then so what? If there is an actual problem with racism, I could understand. But this is literally a matter of "the character isn't as dark skinned as the artist would like".

ummmm.... romantic context - whiter? crime context - darker

No. Bright lights, certain colored lights, etc. Along with being in shadows, having things color-shifted for effect (the whole scene, not just the character). And so on. If a character needs to be lighter, they need to be lighter. If a character needs to be darker, they need to be darker. It's purely a shading/color thing.

The editor's "problem" with the art itself could be that the depiction of the character didn't fit her preconceived stereotype

Or it could be a simple matter of "making a slightly lighter tone for the skin blends well with the rest of the colors on the page, leading to more sales". With a darker skinned character needing the rest of the page to be edited to blend nicely.

Is hubski racist because the background is white and green (for my theme)? No. But if the background was black, he overall theme wouldn't work as well, from purely a colors/contrast standpoint.

And I'm fairly certain with other colors this happens to.

The artist saw the story from his point of view. The editor saw it differently. It's a racial thing, but I could be wrong.

I didn't see it as a racial thing in the slightest. I saw it as "these colors are inaccurate and don't blend well, please brighten them up". Unless, of course, this was a book wide change (every single panel/page), along with future changes to the character being made permanent (that particular skin tone change, rather than just the blending on a few pages).

Again, it might be a racial issue. Sure. But if it is, first, who cares? It's media. Fiction. And second, if it's what sells, it's what sells.

I'm pretty sure "Politically Correct Human" isn't a top seller.

Either way, like most racial/gender things, it's a non-issue that's blown out of proportion for media coverage.