V4.beta Dropdown menu focus/hover style constrast too low for accessibility

Created by: tmorehouse

The current :focus / :hover styling is almost impossible to see (on some screens) as it is a very subtle change.

I would recommend that the background be darkened slightly to make it better for keyboard-only users to know which .dropdown-item they have highlighted.

In this screen shot, I have Another Item focused, and at quick glance (without straining my eyes) I can't tell which menu item is focused:

Doing the same thing, but adjusting the background color from background-color:#f8f9f8 to background-color:#e8e9e8 makes a big difference in being able to tell which menu item has focus: