So if I understand this debate on the Crystal Gems being “people of color”…
It’s more about the Gems being just that, Gems. They’re of a non-binary gender, are sexless, and their race is Crystal Gem. Most of Amethyst’s transformations are either human men or animals, because that’s what form she chooses to take. In the context of the show, their physical forms are only necessary for performing their roles.
I can also see why people say that they are women of color and that is how they appear in the show. And yes, I think it’s great that the Gems aren’t just carbon copies and each of them have physical diversity among one another. And they also refer to each other and identify as female. The character designers gave them features of other ethnicities. Also, aside from Steven, the main Crystal Gems themselves have non-white, female voice actors. So you do have that representation as you watch the show.
But the Gems do not consider themselves human, and never have in the show. Because they’re just Gems. The only Gem that happens to have a sex and gender is Steven since he is half human. The show itself is not color-blind, nor is it erasing race/ethnicity or gender. It explained how Gem culture works.
Though the show does not make an emphasis on what their race is because it does not drive the plot in any way. The Gems do not have to fulfill a trope/stereotype associated with a race, gender or body type to authenticate their appearance or character. There is no distinction of importance on what race they are within the show. There are no white, brown or black Gems, they are Gems and refer to each other as such in the show.
TL;DR: I do believe the creators of the show chose what kind of features they wanted each Gem to have, and which voice actor best fits the character based on their appearance. And that is nice to have that visible representation of more than just “white” cast members. The Gems do not discriminate one another based on appearance or ethnicity, they view each other as a collective species/race in the show. The importance is the content of their character and not just their physical appearance.
Though the show does not make an emphasis on what their race is because it does not drive the plot in any way.
The way that Tumblr has reacted, THIS is what they want but considering that they’re not experts on racial issues either, I would hate to see how they would handle this because in the end, I think they would end up making EVERYONE in the show stereotypes despite crying that’s what they’re against.