That's not to suggest we've reached any level of racial parity in our culture, but only to point out that today, in 2014, it's not particularly unusual to see a people of color in positions of power. When Black parents tell their children they can grow up to be anything they want, they can point to very real examples in pretty much every profession.
That wasn't the case in 1953. Jackie Robinson had only broken the color barrier in professional baseball in 1947. It wouldn't be until 1966 that Robert C. Henry became the first Black mayor of a U.S. city. So the very idea of the protagonist being Black in "Judgment Day!" was novel; the "hero" of every story was a white man back in 1953. "White male" was very much the default for everything, so putting a Black man front and center in this story -- this story about prejudice based on superficial qualities -- said something very powerful. The character, up until the very last panel, would have been assumed to have been a white male and taking off his helmet to reveal otherwise was very much a story twist.
Particularly with the casual way it's done. Read the script closely. It does cite the color of his skin in the text, but merely as a description of his visible appearance; there's no comment or even hint of a suggestion at any cultural baggage based on his skin color. That is only brought to the table by the reader in the context of the times it was written. It's only in the backdrop of 1953 that his skin color holds any real significance.
So does "Judgment Day!" hold up in 2014? Is it still relevant beyond it's historical significance? The original story was aimed at kids in the 1953; would their contemporary counterparts get it? Or would they get to the end, shrug and say, "So he just leaves? What the heck kind of ending is that?"
Or am I too optimistic in that thinking? There were, after all, any number of idiots who complained about Super Bowl advertisements that featured non-Caucasians. Would they still get that same 1953 impact if they read "Judgment Day!" today? I don't have any kids and make a point not to spend any time with racist asshats, but if you have access to either, try printing out those seven pages and ask them to read it in front of you. I'm honestly curious what their reaction would be.