That's grey on a white background. This is what it would look like if it was black (I removed the "color: rgba(0,0,0,75)" tag via chrome's inspector): http://i.imgur.com/v491foi.png

It looks like your rendering (resolution, dpi, hinting? no idea) mitigates the effects of the reduced contrast in a way that mine do not. I'm guessing that's true on their developers' systems as well.