Is your enhancement related to a problem? Please describe.
Check focus styles, also in Windows high contrast mode. I didn't have windows to test at the moment but that should be done.

Also in Firefox 68.0.2 I didn't see focus styles at all. Could be my browser settings but it's usually good to enhance browser default focus styles.

Describe the solution you'd like
Perhaps set same focus and hover styles as in Gutenberg buttons itself. Those have been tested in many different platforms and browsers.

This would need some more investigating and testing.