How to change background color of a menu item when hovering on

Hello,

I have just created the menu of my web site. Under data, I have set Source to None and I have created a custom class to customize the menu items.

I have customized the text color of the menu items and when hovering on each menu item, I would like a different background color.

So I have customized the background color of the created custom class but it does not work! On the contrary, if I choose to underline the menu item when hovering on that, it does work.

What mistake am I making?

Please help!
Thanks,
dan