How do I customize the hover background color of the tabs in the member profile?

[tcarr9]

When looking at a member's profile page, if I hover over the active tab the link color changes but not the background. If I hover over a different tab, both the link color and the background change, to what is either the same color or very similar colors, making it impossible to read the name of the tab.

How can I change either the background color or the link color (either one will do) when hovering over these tabs? This doesn't appear to be a style var, at least not an obvious one. I've had problems with other places where I hover over a tab or button that had to be fixed by adding a few lines to additional.css, but I wouldn't know how to guess what to add there for this.