Okay so I've tried the
:hover .forum-category-wrapper .forum-category-forum {
background-color: #545b75;
color: #fff;
}
And while it changes the colour, I hover anywhere over the actual page the whole forum section changes to the hover colour. Cursor not on page: https://gyazo.com/d39385bae7f75f652f58d2132b3cb406
So it ends up looking like this when you hover over the actual page itself and then when you over the forum sections it turns white: https://gyazo.com/e2d3ee2d9afe2956d9aa703d0e0f9f36