Answer:
Langston Hughes used the denotative meaning of the word uniform ironically "I wear a U.S uniform", to say he wears the uniform of a soldier in battle, but to proof a point of him being black. He asks if after war, without his uniform, when he is still black, if we would be safe.
Step-by-step explanation:
The common meaning of wearing a U.S uniform is used ironically, because this is a poem that talks about war. In war soldiers use uniforms in order to identify one army from the other. But besides wearing that uniform and being that soldier, he is black.
He wonders, what would happened to him when war ends, when he still has his black skin. If it would be a day for him too. If after the war, would "he still be colored slaved"