Update the hero section color

[osbre]

I think it improves the contrast of syntax highlighting colors?

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[garazdawi]

I agree that the syntax highlighting looks better with that background. I’m a bit hesitant to introduce another color to the site though as I think the current colors create a nice uniformity.

Would it be possible to adjust the greyscale of the current banner to make it look better? Or maybe what we should do is adjust the syntax highlighting?