What are some themes in Langston Hughes poetry?

He wrote one (though I'm not sure of the name) that went like this:

Oh God of dust and rainbows, help us see

That without dust the rainbow would not be.

I know it's short, however, when you think about it, it's rather profound. The theme is pretty much that even though bad things happen, good can come out of them. Just like how you can't see a rainbow until it rains.