They are not. It's not just the colors but the visual style. They are different for all three. Conclusion is > have a top bar .. with distinct visual style.

> If you want to make an application that people use all day, having a unique UI is probably not a win.

Not discussing user interface design, it's about visual style. Button should look like a button, but not so much like other site that user confuses your site with someone else's.

>Consistency itself can be beautiful.

Yes, same with search engines, if you used Google you can use Yahoo. But still their visual design is different in many ways if not search result. You can tell Yahoo from Google but not two Bootstrap sites.

Consistency is good for usability. Again, Button should look like a button, but not so much like other site that user confuses your site with someone else's.